diff --git a/DESCRIPTION b/DESCRIPTION
index b2a148ab0..b5f2b0b5b 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Type: Package
 Package: bayestestR
 Title: Understand and Describe Bayesian Models and Posterior Distributions
-Version: 0.14.0.4
+Version: 0.14.0.5
 Authors@R:
     c(person(given = "Dominique",
              family = "Makowski",
@@ -66,7 +66,7 @@ Description: Provides utilities to describe posterior
 Depends:
     R (>= 3.6)
 Imports:
-    insight (>= 0.20.1),
+    insight (>= 0.20.4.2),
     datawizard (>= 0.10.0),
     graphics,
     methods,
@@ -95,6 +95,7 @@ Suggests:
     lavaan,
     lme4,
     logspline (>= 2.1.21),
+    marginaleffects (>= 0.21.0),
     MASS,
     mclust,
     mediation,
@@ -126,3 +127,4 @@ Config/testthat/parallel: true
 Config/rcmdcheck/ignore-inconsequential-notes: true
 Config/Needs/website: easystats/easystatstemplate
 Config/Needs/check: stan-dev/cmdstanr
+Remotes: easystats/insight
diff --git a/NAMESPACE b/NAMESPACE
index f52947612..76db6d047 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -37,22 +37,28 @@ S3method(bayesfactor_models,stanreg)
 S3method(bayesfactor_parameters,bayesfactor_models)
 S3method(bayesfactor_parameters,blavaan)
 S3method(bayesfactor_parameters,brmsfit)
+S3method(bayesfactor_parameters,comparisons)
 S3method(bayesfactor_parameters,data.frame)
 S3method(bayesfactor_parameters,draws)
 S3method(bayesfactor_parameters,emmGrid)
 S3method(bayesfactor_parameters,emm_list)
 S3method(bayesfactor_parameters,numeric)
+S3method(bayesfactor_parameters,predictions)
 S3method(bayesfactor_parameters,rvar)
 S3method(bayesfactor_parameters,sim)
 S3method(bayesfactor_parameters,sim.merMod)
+S3method(bayesfactor_parameters,slopes)
 S3method(bayesfactor_parameters,stanreg)
 S3method(bayesfactor_restricted,blavaan)
 S3method(bayesfactor_restricted,brmsfit)
+S3method(bayesfactor_restricted,comparisons)
 S3method(bayesfactor_restricted,data.frame)
 S3method(bayesfactor_restricted,draws)
 S3method(bayesfactor_restricted,emmGrid)
 S3method(bayesfactor_restricted,emm_list)
+S3method(bayesfactor_restricted,predictions)
 S3method(bayesfactor_restricted,rvar)
+S3method(bayesfactor_restricted,slopes)
 S3method(bayesfactor_restricted,stanreg)
 S3method(bci,BFBayesFactor)
 S3method(bci,BGGM)
@@ -63,6 +69,7 @@ S3method(bci,bcplm)
 S3method(bci,blavaan)
 S3method(bci,blrm)
 S3method(bci,brmsfit)
+S3method(bci,comparisons)
 S3method(bci,data.frame)
 S3method(bci,draws)
 S3method(bci,emmGrid)
@@ -71,9 +78,11 @@ S3method(bci,get_predicted)
 S3method(bci,mcmc)
 S3method(bci,mcmc.list)
 S3method(bci,numeric)
+S3method(bci,predictions)
 S3method(bci,rvar)
 S3method(bci,sim)
 S3method(bci,sim.merMod)
+S3method(bci,slopes)
 S3method(bci,stanfit)
 S3method(bci,stanreg)
 S3method(check_prior,blavaan)
@@ -87,6 +96,7 @@ S3method(ci,bcplm)
 S3method(ci,blavaan)
 S3method(ci,blrm)
 S3method(ci,brmsfit)
+S3method(ci,comparisons)
 S3method(ci,data.frame)
 S3method(ci,draws)
 S3method(ci,emmGrid)
@@ -95,9 +105,11 @@ S3method(ci,get_predicted)
 S3method(ci,mcmc)
 S3method(ci,mcmc.list)
 S3method(ci,numeric)
+S3method(ci,predictions)
 S3method(ci,rvar)
 S3method(ci,sim)
 S3method(ci,sim.merMod)
+S3method(ci,slopes)
 S3method(ci,stanfit)
 S3method(ci,stanreg)
 S3method(cwi,data.frame)
@@ -110,6 +122,7 @@ S3method(describe_posterior,bcplm)
 S3method(describe_posterior,blavaan)
 S3method(describe_posterior,blrm)
 S3method(describe_posterior,brmsfit)
+S3method(describe_posterior,comparisons)
 S3method(describe_posterior,data.frame)
 S3method(describe_posterior,default)
 S3method(describe_posterior,double)
@@ -121,9 +134,11 @@ S3method(describe_posterior,get_predicted)
 S3method(describe_posterior,mcmc)
 S3method(describe_posterior,mcmc.list)
 S3method(describe_posterior,numeric)
+S3method(describe_posterior,predictions)
 S3method(describe_posterior,rvar)
 S3method(describe_posterior,sim)
 S3method(describe_posterior,sim.merMod)
+S3method(describe_posterior,slopes)
 S3method(describe_posterior,stanfit)
 S3method(describe_posterior,stanmvreg)
 S3method(describe_posterior,stanreg)
@@ -157,6 +172,7 @@ S3method(equivalence_test,bcplm)
 S3method(equivalence_test,blavaan)
 S3method(equivalence_test,blrm)
 S3method(equivalence_test,brmsfit)
+S3method(equivalence_test,comparisons)
 S3method(equivalence_test,data.frame)
 S3method(equivalence_test,default)
 S3method(equivalence_test,draws)
@@ -165,9 +181,11 @@ S3method(equivalence_test,emm_list)
 S3method(equivalence_test,mcmc)
 S3method(equivalence_test,mcmc.list)
 S3method(equivalence_test,numeric)
+S3method(equivalence_test,predictions)
 S3method(equivalence_test,rvar)
 S3method(equivalence_test,sim)
 S3method(equivalence_test,sim.merMod)
+S3method(equivalence_test,slopes)
 S3method(equivalence_test,stanfit)
 S3method(equivalence_test,stanreg)
 S3method(estimate_density,BGGM)
@@ -178,6 +196,7 @@ S3method(estimate_density,bcplm)
 S3method(estimate_density,blavaan)
 S3method(estimate_density,blrm)
 S3method(estimate_density,brmsfit)
+S3method(estimate_density,comparisons)
 S3method(estimate_density,data.frame)
 S3method(estimate_density,default)
 S3method(estimate_density,double)
@@ -188,7 +207,9 @@ S3method(estimate_density,grouped_df)
 S3method(estimate_density,mcmc)
 S3method(estimate_density,mcmc.list)
 S3method(estimate_density,numeric)
+S3method(estimate_density,predictions)
 S3method(estimate_density,rvar)
+S3method(estimate_density,slopes)
 S3method(estimate_density,stanfit)
 S3method(estimate_density,stanreg)
 S3method(eti,BFBayesFactor)
@@ -200,6 +221,7 @@ S3method(eti,bcplm)
 S3method(eti,blavaan)
 S3method(eti,blrm)
 S3method(eti,brmsfit)
+S3method(eti,comparisons)
 S3method(eti,data.frame)
 S3method(eti,default)
 S3method(eti,draws)
@@ -209,9 +231,11 @@ S3method(eti,get_predicted)
 S3method(eti,mcmc)
 S3method(eti,mcmc.list)
 S3method(eti,numeric)
+S3method(eti,predictions)
 S3method(eti,rvar)
 S3method(eti,sim)
 S3method(eti,sim.merMod)
+S3method(eti,slopes)
 S3method(eti,stanfit)
 S3method(eti,stanreg)
 S3method(format,bayesfactor_inclusion)
@@ -239,6 +263,7 @@ S3method(hdi,bcplm)
 S3method(hdi,blavaan)
 S3method(hdi,blrm)
 S3method(hdi,brmsfit)
+S3method(hdi,comparisons)
 S3method(hdi,data.frame)
 S3method(hdi,default)
 S3method(hdi,draws)
@@ -248,9 +273,11 @@ S3method(hdi,get_predicted)
 S3method(hdi,mcmc)
 S3method(hdi,mcmc.list)
 S3method(hdi,numeric)
+S3method(hdi,predictions)
 S3method(hdi,rvar)
 S3method(hdi,sim)
 S3method(hdi,sim.merMod)
+S3method(hdi,slopes)
 S3method(hdi,stanfit)
 S3method(hdi,stanreg)
 S3method(map_estimate,BGGM)
@@ -260,6 +287,7 @@ S3method(map_estimate,bcplm)
 S3method(map_estimate,blavaan)
 S3method(map_estimate,blrm)
 S3method(map_estimate,brmsfit)
+S3method(map_estimate,comparisons)
 S3method(map_estimate,data.frame)
 S3method(map_estimate,draws)
 S3method(map_estimate,emmGrid)
@@ -268,7 +296,9 @@ S3method(map_estimate,get_predicted)
 S3method(map_estimate,mcmc)
 S3method(map_estimate,mcmc.list)
 S3method(map_estimate,numeric)
+S3method(map_estimate,predictions)
 S3method(map_estimate,rvar)
+S3method(map_estimate,slopes)
 S3method(map_estimate,stanfit)
 S3method(map_estimate,stanreg)
 S3method(mcse,blavaan)
@@ -287,6 +317,7 @@ S3method(p_direction,bcplm)
 S3method(p_direction,blavaan)
 S3method(p_direction,blrm)
 S3method(p_direction,brmsfit)
+S3method(p_direction,comparisons)
 S3method(p_direction,data.frame)
 S3method(p_direction,default)
 S3method(p_direction,draws)
@@ -297,9 +328,11 @@ S3method(p_direction,mcmc)
 S3method(p_direction,mcmc.list)
 S3method(p_direction,numeric)
 S3method(p_direction,parameters_model)
+S3method(p_direction,predictions)
 S3method(p_direction,rvar)
 S3method(p_direction,sim)
 S3method(p_direction,sim.merMod)
+S3method(p_direction,slopes)
 S3method(p_direction,stanfit)
 S3method(p_direction,stanreg)
 S3method(p_map,BFBayesFactor)
@@ -311,6 +344,7 @@ S3method(p_map,bcplm)
 S3method(p_map,blavaan)
 S3method(p_map,blrm)
 S3method(p_map,brmsfit)
+S3method(p_map,comparisons)
 S3method(p_map,data.frame)
 S3method(p_map,draws)
 S3method(p_map,emmGrid)
@@ -319,9 +353,11 @@ S3method(p_map,get_predicted)
 S3method(p_map,mcmc)
 S3method(p_map,mcmc.list)
 S3method(p_map,numeric)
+S3method(p_map,predictions)
 S3method(p_map,rvar)
 S3method(p_map,sim)
 S3method(p_map,sim.merMod)
+S3method(p_map,slopes)
 S3method(p_map,stanfit)
 S3method(p_map,stanreg)
 S3method(p_rope,BFBayesFactor)
@@ -332,6 +368,7 @@ S3method(p_rope,bcplm)
 S3method(p_rope,blavaan)
 S3method(p_rope,blrm)
 S3method(p_rope,brmsfit)
+S3method(p_rope,comparisons)
 S3method(p_rope,data.frame)
 S3method(p_rope,default)
 S3method(p_rope,draws)
@@ -340,9 +377,11 @@ S3method(p_rope,emm_list)
 S3method(p_rope,mcmc)
 S3method(p_rope,mcmc.list)
 S3method(p_rope,numeric)
+S3method(p_rope,predictions)
 S3method(p_rope,rvar)
 S3method(p_rope,sim)
 S3method(p_rope,sim.merMod)
+S3method(p_rope,slopes)
 S3method(p_rope,stanfit)
 S3method(p_rope,stanreg)
 S3method(p_significance,BFBayesFactor)
@@ -354,6 +393,7 @@ S3method(p_significance,bcplm)
 S3method(p_significance,blavaan)
 S3method(p_significance,blrm)
 S3method(p_significance,brmsfit)
+S3method(p_significance,comparisons)
 S3method(p_significance,data.frame)
 S3method(p_significance,default)
 S3method(p_significance,draws)
@@ -364,7 +404,9 @@ S3method(p_significance,mcmc)
 S3method(p_significance,mcmc.list)
 S3method(p_significance,numeric)
 S3method(p_significance,parameters_simulate_model)
+S3method(p_significance,predictions)
 S3method(p_significance,rvar)
+S3method(p_significance,slopes)
 S3method(p_significance,stanfit)
 S3method(p_significance,stanreg)
 S3method(p_to_bf,default)
@@ -396,6 +438,7 @@ S3method(point_estimate,bcplm)
 S3method(point_estimate,blavaan)
 S3method(point_estimate,blrm)
 S3method(point_estimate,brmsfit)
+S3method(point_estimate,comparisons)
 S3method(point_estimate,data.frame)
 S3method(point_estimate,default)
 S3method(point_estimate,draws)
@@ -406,9 +449,11 @@ S3method(point_estimate,matrix)
 S3method(point_estimate,mcmc)
 S3method(point_estimate,mcmc.list)
 S3method(point_estimate,numeric)
+S3method(point_estimate,predictions)
 S3method(point_estimate,rvar)
 S3method(point_estimate,sim)
 S3method(point_estimate,sim.merMod)
+S3method(point_estimate,slopes)
 S3method(point_estimate,stanfit)
 S3method(point_estimate,stanreg)
 S3method(print,bayesfactor_inclusion)
@@ -469,6 +514,7 @@ S3method(rope,bcplm)
 S3method(rope,blavaan)
 S3method(rope,blrm)
 S3method(rope,brmsfit)
+S3method(rope,comparisons)
 S3method(rope,data.frame)
 S3method(rope,default)
 S3method(rope,draws)
@@ -478,9 +524,11 @@ S3method(rope,get_predicted)
 S3method(rope,mcmc)
 S3method(rope,mcmc.list)
 S3method(rope,numeric)
+S3method(rope,predictions)
 S3method(rope,rvar)
 S3method(rope,sim)
 S3method(rope,sim.merMod)
+S3method(rope,slopes)
 S3method(rope,stanfit)
 S3method(rope,stanreg)
 S3method(rope_range,data.frame)
@@ -512,13 +560,16 @@ S3method(sexit_thresholds,wbm)
 S3method(sexit_thresholds,zeroinfl)
 S3method(si,blavaan)
 S3method(si,brmsfit)
+S3method(si,comparisons)
 S3method(si,data.frame)
 S3method(si,draws)
 S3method(si,emmGrid)
 S3method(si,emm_list)
 S3method(si,get_predicted)
 S3method(si,numeric)
+S3method(si,predictions)
 S3method(si,rvar)
+S3method(si,slopes)
 S3method(si,stanfit)
 S3method(si,stanreg)
 S3method(simulate_prior,bcplm)
@@ -534,16 +585,21 @@ S3method(spi,bcplm)
 S3method(spi,blavaan)
 S3method(spi,blrm)
 S3method(spi,brmsfit)
+S3method(spi,comparisons)
 S3method(spi,data.frame)
 S3method(spi,default)
+S3method(spi,draws)
 S3method(spi,emmGrid)
 S3method(spi,emm_list)
 S3method(spi,get_predicted)
 S3method(spi,mcmc)
 S3method(spi,mcmc.list)
 S3method(spi,numeric)
+S3method(spi,predictions)
+S3method(spi,rvar)
 S3method(spi,sim)
 S3method(spi,sim.merMod)
+S3method(spi,slopes)
 S3method(spi,stanfit)
 S3method(spi,stanreg)
 S3method(unupdate,blavaan)
diff --git a/NEWS.md b/NEWS.md
index d6e5dc464..3eebdf519 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -2,6 +2,11 @@
 
 ## Changes
 
+* Added support for `{marginaleffects}`
+
+* Results from objects generated by `{emmeans}` (`emmGrid`/`emm_list`) now
+  return results with appended grid-data. 
+
 * Usability improvements for `p_direction()`:
 
   - Results from `p_direction()` can directly be used in `pd_to_p()`.
diff --git a/R/bayesfactor_parameters.R b/R/bayesfactor_parameters.R
index 6e1b2e832..f11f9c665 100644
--- a/R/bayesfactor_parameters.R
+++ b/R/bayesfactor_parameters.R
@@ -94,6 +94,9 @@
 #'       - `prior` can also be a model equivalent to `posterior` but with samples from
 #'         the priors *only*. See [unupdate()].
 #'       - **Note:** When `posterior` is a `brmsfit_multiple` model, `prior` **must** be provided.
+#'   - When `posterior` is an output from a `{marginaleffects}` function, `prior` should also be an an output
+#'   from a `{marginaleffects}` function equivalent to `posterior` but created
+#'   with a model of priors samples *only*.
 #'   - When `posterior` is an `emmGrid` / `emm_list` object:
 #'       - `prior` should also be an `emmGrid` / `emm_list` object equivalent to `posterior` but
 #'        created with a model of priors samples *only*. See [unupdate()].
@@ -378,7 +381,7 @@ bayesfactor_parameters.emmGrid <- function(posterior,
   )
 
   # Get BFs
-  bayesfactor_parameters.data.frame(
+  out <- bayesfactor_parameters.data.frame(
     posterior = samps$posterior,
     prior = samps$prior,
     direction = direction,
@@ -386,11 +389,21 @@ bayesfactor_parameters.emmGrid <- function(posterior,
     verbose = verbose,
     ...
   )
+  .append_datagrid(out, posterior)
 }
 
 #' @export
 bayesfactor_parameters.emm_list <- bayesfactor_parameters.emmGrid
 
+#' @export
+bayesfactor_parameters.slopes <- bayesfactor_parameters.emmGrid
+
+#' @export
+bayesfactor_parameters.predictions <- bayesfactor_parameters.emmGrid
+
+#' @export
+bayesfactor_parameters.comparisons <- bayesfactor_parameters.emmGrid
+
 
 #' @rdname bayesfactor_parameters
 #' @export
diff --git a/R/bayesfactor_restricted.R b/R/bayesfactor_restricted.R
index 4e8cef5f2..c5ddf4f46 100644
--- a/R/bayesfactor_restricted.R
+++ b/R/bayesfactor_restricted.R
@@ -185,6 +185,15 @@ bayesfactor_restricted.emmGrid <- function(posterior, hypothesis, prior = NULL,
 #' @export
 bayesfactor_restricted.emm_list <- bayesfactor_restricted.emmGrid
 
+#' @export
+bayesfactor_restricted.slopes <- bayesfactor_restricted.emmGrid
+
+#' @export
+bayesfactor_restricted.predictions <- bayesfactor_restricted.emmGrid
+
+#' @export
+bayesfactor_restricted.comparisons <- bayesfactor_restricted.emmGrid
+
 #' @export
 bayesfactor_restricted.data.frame <- function(posterior, hypothesis, prior = NULL, ...) {
   p_hypothesis <- parse(text = hypothesis)
diff --git a/R/bci.R b/R/bci.R
index 51f5c2b28..190c229c6 100644
--- a/R/bci.R
+++ b/R/bci.R
@@ -167,8 +167,8 @@ bci.sim <- function(x, ci = 0.95, parameters = NULL, verbose = TRUE, ...) {
 #' @export
 bci.emmGrid <- function(x, ci = 0.95, verbose = TRUE, ...) {
   xdf <- insight::get_parameters(x)
-
   dat <- bci(xdf, ci = ci, verbose = verbose, ...)
+  dat <- .append_datagrid(dat, x)
   attr(dat, "object_name") <- insight::safe_deparse_symbol(substitute(x))
   dat
 }
@@ -176,6 +176,22 @@ bci.emmGrid <- function(x, ci = 0.95, verbose = TRUE, ...) {
 #' @export
 bci.emm_list <- bci.emmGrid
 
+#' @rdname bci
+#' @export
+bci.slopes <- function(x, ci = 0.95, verbose = TRUE, ...) {
+  xrvar <- .get_marginaleffects_draws(x)
+  dat <- bci(xrvar, ci = ci, verbose = verbose, ...)
+  dat <- .append_datagrid(dat, x)
+  attr(dat, "object_name") <- insight::safe_deparse_symbol(substitute(x))
+  dat
+}
+
+#' @export
+bci.comparisons <- bci.slopes
+
+#' @export
+bci.predictions <- bci.slopes
+
 #' @rdname bci
 #' @export
 bci.stanreg <- function(x,
@@ -300,8 +316,8 @@ bci.get_predicted <- function(x, ci = 0.95, use_iterations = FALSE, verbose = TR
   upper <- stats::quantile(x, upper.inv, names = FALSE, na.rm = TRUE)
 
   data.frame(
-    "CI" = ci,
-    "CI_low" = lower,
-    "CI_high" = upper
+    CI = ci,
+    CI_low = lower,
+    CI_high = upper
   )
 }
diff --git a/R/ci.R b/R/ci.R
index cdc5d9eb9..be5e91f05 100644
--- a/R/ci.R
+++ b/R/ci.R
@@ -172,21 +172,44 @@ ci.rvar <- ci.draws
 
 #' @export
 ci.emmGrid <- function(x, ci = NULL, ...) {
-  if (!.is_baysian_emmeans(x)) {
+  if (!.is_baysian_grid(x)) {
     insight::check_if_installed("parameters")
     if (is.null(ci)) ci <- 0.95
     return(parameters::ci(model = x, ci = ci, ...))
   }
 
   if (is.null(ci)) ci <- 0.95
-  x <- insight::get_parameters(x)
-  ci(x, ci = ci, ...)
+  xdf <- insight::get_parameters(x)
+  out <- ci(xdf, ci = ci, ...)
+  out <- .append_datagrid(out, x)
+  out
 }
 
 
 #' @export
 ci.emm_list <- ci.emmGrid
 
+#' @export
+ci.slopes <- function(x, ci = NULL, ...) {
+  if (!.is_baysian_grid(x)) {
+    insight::check_if_installed("parameters")
+    if (is.null(ci)) ci <- 0.95
+    return(parameters::ci(model = x, ci = ci, ...))
+  }
+
+  if (is.null(ci)) ci <- 0.95
+  xrvar <- .get_marginaleffects_draws(x)
+  out <- ci(xrvar, ci = ci, ...)
+  out <- .append_datagrid(out, x)
+  out
+}
+
+#' @export
+ci.comparisons <- ci.slopes
+
+#' @export
+ci.predictions <- ci.slopes
+
 
 #' @rdname ci
 #' @export
diff --git a/R/describe_posterior.R b/R/describe_posterior.R
index 3e8d82209..56b3c8432 100644
--- a/R/describe_posterior.R
+++ b/R/describe_posterior.R
@@ -655,7 +655,7 @@ describe_posterior.draws <- function(posterior,
     rope_range = rope_range,
     rope_ci = rope_ci,
     keep_iterations = keep_iterations,
-    bf_prior = bf_prior,
+    bf_prior = if (!is.null(bf_prior)) .posterior_draws_to_df(bf_prior),
     BF = BF,
     verbose = verbose,
     ...
@@ -794,7 +794,6 @@ describe_posterior.emmGrid <- function(posterior,
     posterior_samples <- insight::get_parameters(posterior)
   }
 
-
   out <- .describe_posterior(
     posterior_samples,
     centrality = centrality,
@@ -812,11 +811,10 @@ describe_posterior.emmGrid <- function(posterior,
   )
 
   row.names(out) <- NULL # Reset row names
-
+  out <- .append_datagrid(out, posterior)
   class(out) <- c("describe_posterior", "see_describe_posterior", class(out))
   attr(out, "ci_method") <- ci_method
   attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(posterior))
-
   out
 }
 
@@ -824,7 +822,58 @@ describe_posterior.emmGrid <- function(posterior,
 #' @export
 describe_posterior.emm_list <- describe_posterior.emmGrid
 
+#' @export
+describe_posterior.slopes <- function(posterior,
+                                      centrality = "median",
+                                      dispersion = FALSE,
+                                      ci = 0.95,
+                                      ci_method = "eti",
+                                      test = c("p_direction", "rope"),
+                                      rope_range = "default",
+                                      rope_ci = 0.95,
+                                      keep_iterations = FALSE,
+                                      bf_prior = NULL,
+                                      BF = 1,
+                                      verbose = TRUE,
+                                      ...) {
+  if (any(c("all", "bf", "bayesfactor", "bayes_factor") %in% tolower(test)) ||
+    "si" %in% tolower(ci_method)) {
+    samps <- .clean_priors_and_posteriors(posterior, bf_prior, verbose = verbose)
+    bf_prior <- samps$prior
+    posterior_samples <- samps$posterior
+  } else {
+    posterior_samples <- .get_marginaleffects_draws(posterior)
+  }
 
+  out <- describe_posterior(
+    posterior_samples,
+    centrality = centrality,
+    dispersion = dispersion,
+    ci = ci,
+    ci_method = ci_method,
+    test = test,
+    rope_range = rope_range,
+    rope_ci = rope_ci,
+    keep_iterations = keep_iterations,
+    bf_prior = bf_prior,
+    BF = BF,
+    verbose = verbose,
+    ...
+  )
+
+  row.names(out) <- NULL # Reset row names
+  out <- .append_datagrid(out, posterior)
+  class(out) <- c("describe_posterior", "see_describe_posterior", class(out))
+  attr(out, "ci_method") <- ci_method
+  attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(posterior))
+  out
+}
+
+#' @export
+describe_posterior.comparisons <- describe_posterior.slopes
+
+#' @export
+describe_posterior.predictions <- describe_posterior.slopes
 
 
 # Stan ------------------------------
diff --git a/R/equivalence_test.R b/R/equivalence_test.R
index 99c19e433..163db680d 100644
--- a/R/equivalence_test.R
+++ b/R/equivalence_test.R
@@ -182,8 +182,8 @@ equivalence_test.rvar <- equivalence_test.draws
 #' @export
 equivalence_test.emmGrid <- function(x, range = "default", ci = 0.95, verbose = TRUE, ...) {
   xdf <- insight::get_parameters(x)
-
   out <- equivalence_test(xdf, range = range, ci = ci, verbose = verbose, ...)
+  out <- .append_datagrid(out, x)
   attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
   out
 }
@@ -192,6 +192,22 @@ equivalence_test.emmGrid <- function(x, range = "default", ci = 0.95, verbose =
 equivalence_test.emm_list <- equivalence_test.emmGrid
 
 
+#' @export
+equivalence_test.slopes <- function(x, range = "default", ci = 0.95, verbose = TRUE, ...) {
+  xrvar <- .get_marginaleffects_draws(x)
+  out <- equivalence_test(xrvar, range = range, ci = ci, verbose = verbose, ...)
+  out <- .append_datagrid(out, x)
+  attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
+  out
+}
+
+#' @export
+equivalence_test.comparisons <- equivalence_test.slopes
+
+#' @export
+equivalence_test.predictions <- equivalence_test.slopes
+
+
 #' @export
 equivalence_test.BFBayesFactor <- function(x, range = "default", ci = 0.95, verbose = TRUE, ...) {
   out <- equivalence_test(insight::get_parameters(x), range = range, ci = ci, verbose = verbose, ...)
diff --git a/R/estimate_density.R b/R/estimate_density.R
index 2074c4efc..a8307c37c 100644
--- a/R/estimate_density.R
+++ b/R/estimate_density.R
@@ -367,13 +367,19 @@ estimate_density.emmGrid <- function(x,
                                      extend_scale = 0.1,
                                      bw = "SJ",
                                      ...) {
-  x <- insight::get_parameters(x)
+  xdf <- insight::get_parameters(x)
 
-  out <- estimate_density(x,
+  out <- estimate_density(xdf,
     method = method, precision = precision,
     extend = extend, extend_scale = extend_scale,
     bw = bw, ...
   )
+
+  # This doesn't use .append_datagrid because we get a non-grid output
+  dgrid <- insight::get_datagrid(x)
+  dgrid$Parameter <- unique(out$Parameter)
+  out <- datawizard::data_join(dgrid, out, by = "Parameter")
+  out$Parameter <- NULL
   class(out) <- .set_density_class(out)
   out
 }
@@ -381,6 +387,37 @@ estimate_density.emmGrid <- function(x,
 #' @export
 estimate_density.emm_list <- estimate_density.emmGrid
 
+#' @export
+estimate_density.slopes <- function(x,
+                                    method = "kernel",
+                                    precision = 2^10,
+                                    extend = FALSE,
+                                    extend_scale = 0.1,
+                                    bw = "SJ",
+                                    ...) {
+  xdf <- .get_marginaleffects_draws(x)
+
+  out <- estimate_density(xdf,
+    method = method, precision = precision,
+    extend = extend, extend_scale = extend_scale,
+    bw = bw, ...
+  )
+
+  # This doesn't use .append_datagrid because we get a non-grid output
+  dgrid <- insight::get_datagrid(x)
+  dgrid$Parameter <- unique(out$Parameter)
+  out <- datawizard::data_join(dgrid, out, by = "Parameter")
+  out$Parameter <- NULL
+  class(out) <- .set_density_class(out)
+  out
+}
+
+#' @export
+estimate_density.predictions <- estimate_density.slopes
+
+#' @export
+estimate_density.comparisons <- estimate_density.slopes
+
 
 #' @export
 estimate_density.stanreg <- function(x,
diff --git a/R/eti.R b/R/eti.R
index 73f22c6e8..9e2b64935 100644
--- a/R/eti.R
+++ b/R/eti.R
@@ -174,8 +174,8 @@ eti.sim <- function(x, ci = 0.95, parameters = NULL, verbose = TRUE, ...) {
 #' @export
 eti.emmGrid <- function(x, ci = 0.95, verbose = TRUE, ...) {
   xdf <- insight::get_parameters(x)
-
   dat <- eti(xdf, ci = ci, verbose = verbose, ...)
+  dat <- .append_datagrid(dat, x)
   attr(dat, "object_name") <- insight::safe_deparse_symbol(substitute(x))
   dat
 }
@@ -183,6 +183,20 @@ eti.emmGrid <- function(x, ci = 0.95, verbose = TRUE, ...) {
 #' @export
 eti.emm_list <- eti.emmGrid
 
+#' @export
+eti.slopes <- function(x, ci = 0.95, verbose = TRUE, ...) {
+  xrvar <- .get_marginaleffects_draws(x)
+  dat <- eti(xrvar, ci = ci, verbose = verbose, ...)
+  dat <- .append_datagrid(dat, x)
+  attr(dat, "object_name") <- insight::safe_deparse_symbol(substitute(x))
+  dat
+}
+
+#' @export
+eti.comparisons <- eti.slopes
+
+#' @export
+eti.predictions <- eti.slopes
 
 #' @rdname eti
 #' @export
diff --git a/R/format.R b/R/format.R
index c5e21f5b9..3d81e4734 100644
--- a/R/format.R
+++ b/R/format.R
@@ -103,7 +103,8 @@ format.bayesfactor_models <- function(x,
   BFE$log_BF <- as.numeric(x, log = log)
   BFE$BF <- insight::format_bf(abs(BFE$log_BF), name = NULL, exact = exact, ...)
 
-  if (any((sgn <- sign(BFE$log_BF) < 0)[!is.na(BFE$log_BF)])) {
+  sgn <- sign(BFE$log_BF)
+  if (any((sgn < 0)[!is.na(BFE$log_BF)])) {
     BFE$BF[sgn] <- paste0("-", BFE$BF[sgn])
   }
 
@@ -170,7 +171,8 @@ format.bayesfactor_inclusion <- function(x,
   BFE$log_BF <- as.numeric(x, log = log)
   BFE$BF <- insight::format_bf(abs(BFE$log_BF), name = NULL, exact = exact, ...)
 
-  if (any((sgn <- sign(BFE$log_BF) < 0)[!is.na(BFE$log_BF)])) {
+  sgn <- sign(BFE$log_BF)
+  if (any((sgn < 0)[!is.na(BFE$log_BF)])) {
     BFE$BF[sgn] <- paste0("-", BFE$BF[sgn])
   }
 
@@ -221,11 +223,13 @@ format.bayesfactor_restricted <- function(x,
   BFE$log_BF <- as.numeric(x, log = log)
   BFE$BF <- insight::format_bf(abs(BFE$log_BF), name = NULL, exact = exact, ...)
 
-  if (any((sgn <- sign(BFE$log_BF) < 0)[!is.na(BFE$log_BF)])) {
+  sgn <- sign(BFE$log_BF)
+  if (any((sgn < 0)[!is.na(BFE$log_BF)])) {
     BFE$BF[sgn] <- paste0("-", BFE$BF[sgn])
   }
   BFE$log_BF <- NULL
-  colnames(BFE) <- c("Hypothesis", "P(Prior)", "P(Posterior)", "BF")
+  colnames(BFE)[colnames(BFE) == "p_prior"] <- "P(Prior)"
+  colnames(BFE)[colnames(BFE) == "p_posterior"] <- "P(Posterior)"
 
   # footer
   if (is.null(format) || format == "text") {
@@ -266,7 +270,8 @@ format.bayesfactor_parameters <- function(x,
 
   x$BF_override <- insight::format_bf(abs(x$log_BF), name = NULL, exact = exact, ...)
 
-  if (any((sgn <- sign(x$log_BF) < 0)[!is.na(x$log_BF)])) {
+  sgn <- sign(x$log_BF)
+  if (any((sgn < 0)[!is.na(x$log_BF)])) {
     x$BF_override[sgn] <- paste0("-", x$BF_override[sgn])
   }
   x$log_BF <- NULL
diff --git a/R/hdi.R b/R/hdi.R
index 01dc5bc0b..bf1aa4244 100644
--- a/R/hdi.R
+++ b/R/hdi.R
@@ -264,6 +264,7 @@ hdi.sim <- function(x, ci = 0.95, parameters = NULL, verbose = TRUE, ...) {
 hdi.emmGrid <- function(x, ci = 0.95, verbose = TRUE, ...) {
   xdf <- insight::get_parameters(x)
   out <- hdi(xdf, ci = ci, verbose = verbose, ...)
+  out <- .append_datagrid(out, x)
   attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
   out
 }
@@ -271,6 +272,21 @@ hdi.emmGrid <- function(x, ci = 0.95, verbose = TRUE, ...) {
 #' @export
 hdi.emm_list <- hdi.emmGrid
 
+#' @export
+hdi.slopes <- function(x, ci = 0.95, verbose = TRUE, ...) {
+  xrvar <- .get_marginaleffects_draws(x)
+  out <- hdi(xrvar, ci = ci, verbose = verbose, ...)
+  out <- .append_datagrid(out, x)
+  attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
+  out
+}
+
+#' @export
+hdi.comparisons <- hdi.slopes
+
+#' @export
+hdi.predictions <- hdi.slopes
+
 
 #' @rdname hdi
 #' @export
diff --git a/R/map_estimate.R b/R/map_estimate.R
index 2f80c463c..68bfafae0 100644
--- a/R/map_estimate.R
+++ b/R/map_estimate.R
@@ -165,13 +165,27 @@ map_estimate.rvar <- map_estimate.draws
 
 #' @export
 map_estimate.emmGrid <- function(x, precision = 2^10, method = "kernel", ...) {
-  x <- insight::get_parameters(x)
-  .map_estimate_models(x, precision = precision, method = method)
+  xdf <- insight::get_parameters(x)
+  out <- .map_estimate_models(xdf, precision = precision, method = method)
+  .append_datagrid(out, x)
 }
 
 #' @export
 map_estimate.emm_list <- map_estimate.emmGrid
 
+#' @export
+map_estimate.slopes <- function(x, precision = 2^10, method = "kernel", ...) {
+  xrvar <- .get_marginaleffects_draws(x)
+  out <- map_estimate(xrvar, precision = precision, method = method, ...)
+  .append_datagrid(out, x)
+}
+
+#' @export
+map_estimate.comparisons <- map_estimate.slopes
+
+#' @export
+map_estimate.predictions <- map_estimate.slopes
+
 
 #' @rdname map_estimate
 #' @export
diff --git a/R/p_direction.R b/R/p_direction.R
index a733e9339..12e8e05b5 100644
--- a/R/p_direction.R
+++ b/R/p_direction.R
@@ -389,8 +389,8 @@ p_direction.bamlss <- function(x,
 #' @export
 p_direction.emmGrid <- function(x, method = "direct", null = 0, as_p = FALSE, remove_na = TRUE, ...) {
   xdf <- insight::get_parameters(x)
-
   out <- p_direction(xdf, method = method, null = null, as_p = as_p, remove_na = remove_na, ...)
+  out <- .append_datagrid(out, x)
   attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
   out
 }
@@ -399,6 +399,22 @@ p_direction.emmGrid <- function(x, method = "direct", null = 0, as_p = FALSE, re
 #' @export
 p_direction.emm_list <- p_direction.emmGrid
 
+#' @rdname p_direction
+#' @export
+p_direction.slopes <- function(x, method = "direct", null = 0, as_p = FALSE, remove_na = TRUE, ...) {
+  xrvar <- .get_marginaleffects_draws(x)
+  out <- p_direction(xrvar, method = method, null = null, as_p = as_p, remove_na = remove_na, ...)
+  out <- .append_datagrid(out, x)
+  attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
+  out
+}
+
+#' @export
+p_direction.comparisons <- p_direction.slopes
+
+#' @export
+p_direction.predictions <- p_direction.slopes
+
 
 #' @keywords internal
 .p_direction_models <- function(x,
diff --git a/R/p_map.R b/R/p_map.R
index 3e1cd3ef8..60efe1580 100644
--- a/R/p_map.R
+++ b/R/p_map.R
@@ -158,8 +158,8 @@ p_map.rvar <- p_map.draws
 #' @export
 p_map.emmGrid <- function(x, null = 0, precision = 2^10, method = "kernel", ...) {
   xdf <- insight::get_parameters(x)
-
   out <- p_map(xdf, null = null, precision = precision, method = method, ...)
+  out <- .append_datagrid(out, x)
   attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
   out
 }
@@ -167,7 +167,20 @@ p_map.emmGrid <- function(x, null = 0, precision = 2^10, method = "kernel", ...)
 #' @export
 p_map.emm_list <- p_map.emmGrid
 
+#' @export
+p_map.slopes <- function(x, null = 0, precision = 2^10, method = "kernel", ...) {
+  xrvar <- .get_marginaleffects_draws(x)
+  out <- p_map(xrvar, null = null, precision = precision, method = method, ...)
+  out <- .append_datagrid(out, x)
+  attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
+  out
+}
+
+#' @export
+p_map.comparisons <- p_map.slopes
 
+#' @export
+p_map.predictions <- p_map.slopes
 
 
 #' @keywords internal
diff --git a/R/p_rope.R b/R/p_rope.R
index e88f656b6..9b2522228 100644
--- a/R/p_rope.R
+++ b/R/p_rope.R
@@ -53,8 +53,8 @@ p_rope.rvar <- p_rope.draws
 #' @export
 p_rope.emmGrid <- function(x, range = "default", verbose = TRUE, ...) {
   xdf <- insight::get_parameters(x)
-
   out <- p_rope(xdf, range = range, verbose = verbose)
+  out <- .append_datagrid(out, x)
   attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
   out
 }
@@ -62,6 +62,21 @@ p_rope.emmGrid <- function(x, range = "default", verbose = TRUE, ...) {
 #' @export
 p_rope.emm_list <- p_rope.emmGrid
 
+#' @export
+p_rope.slopes <- function(x, range = "default", verbose = TRUE, ...) {
+  xrvar <- .get_marginaleffects_draws(x)
+  out <- p_rope(xrvar, range = range, verbose = verbose)
+  out <- .append_datagrid(out, x)
+  attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
+  out
+}
+
+#' @export
+p_rope.comparisons <- p_rope.slopes
+
+#' @export
+p_rope.predictions <- p_rope.slopes
+
 #' @export
 p_rope.BFBayesFactor <- p_rope.numeric
 
diff --git a/R/p_significance.R b/R/p_significance.R
index c2470caad..68a179fa2 100644
--- a/R/p_significance.R
+++ b/R/p_significance.R
@@ -215,8 +215,8 @@ p_significance.BGGM <- p_significance.bcplm
 #' @export
 p_significance.emmGrid <- function(x, threshold = "default", ...) {
   xdf <- insight::get_parameters(x)
-
   out <- p_significance(xdf, threshold = threshold, ...)
+  out <- .append_datagrid(out, x)
   attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
   out
 }
@@ -224,6 +224,20 @@ p_significance.emmGrid <- function(x, threshold = "default", ...) {
 #' @export
 p_significance.emm_list <- p_significance.emmGrid
 
+#' @export
+p_significance.slopes <- function(x, threshold = "default", ...) {
+  xrvar <- .get_marginaleffects_draws(x)
+  out <- p_significance(xrvar, threshold = threshold, ...)
+  out <- .append_datagrid(out, x)
+  attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
+  out
+}
+
+#' @export
+p_significance.comparisons <- p_significance.slopes
+
+#' @export
+p_significance.predictions <- p_significance.slopes
 
 
 #' @rdname p_significance
diff --git a/R/point_estimate.R b/R/point_estimate.R
index d725749f3..15b305766 100644
--- a/R/point_estimate.R
+++ b/R/point_estimate.R
@@ -220,8 +220,8 @@ point_estimate.MCMCglmm <- function(x, centrality = "all", dispersion = FALSE, .
 #' @export
 point_estimate.emmGrid <- function(x, centrality = "all", dispersion = FALSE, ...) {
   xdf <- insight::get_parameters(x)
-
   out <- point_estimate(xdf, centrality = centrality, dispersion = dispersion, ...)
+  out <- .append_datagrid(out, x)
   attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
   out
 }
@@ -229,6 +229,20 @@ point_estimate.emmGrid <- function(x, centrality = "all", dispersion = FALSE, ..
 #' @export
 point_estimate.emm_list <- point_estimate.emmGrid
 
+#' @export
+point_estimate.slopes <- function(x, centrality = "all", dispersion = FALSE, ...) {
+  xrvar <- .get_marginaleffects_draws(x)
+  out <- point_estimate(xrvar, centrality = centrality, dispersion = dispersion, ...)
+  out <- .append_datagrid(out, x)
+  attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
+  out
+}
+
+#' @export
+point_estimate.comparisons <- point_estimate.slopes
+
+#' @export
+point_estimate.predictions <- point_estimate.slopes
 
 #' @rdname point_estimate
 #' @export
diff --git a/R/print.equivalence_test.R b/R/print.equivalence_test.R
index e9413ddf6..978253fc7 100644
--- a/R/print.equivalence_test.R
+++ b/R/print.equivalence_test.R
@@ -6,7 +6,7 @@ print.equivalence_test <- function(x, digits = 2, ...) {
 
   # fix "sd" pattern
   model <- .retrieve_model(x)
-  if (!is.null(model)) {
+  if (!is.null(model) && !is.data.frame(model)) {
     cp <- insight::clean_parameters(model)
     if (!is.null(cp$Group) && any(startsWith(cp$Group, "SD/Cor"))) {
       cp <- cp[startsWith(cp$Group, "SD/Cor"), ]
@@ -34,7 +34,10 @@ print.equivalence_test <- function(x, digits = 2, ...) {
   x$HDI <- sprintf("[%*s %*s]", maxlen_low, x$HDI_low, maxlen_high, x$HDI_high)
 
   ci <- unique(x$CI)
-  keep.columns <- c("CI", "Parameter", "ROPE_Equivalence", "ROPE_Percentage", "HDI", "Effects", "Component")
+  keep.columns <- c(
+    attr(x, "grid_cols"), "Parameter", "Effects", "Component",
+    "ROPE_Equivalence", "ROPE_Percentage", "CI", "HDI"
+  )
 
   x <- x[, intersect(keep.columns, colnames(x))]
 
diff --git a/R/print.rope.R b/R/print.rope.R
index 85d21cd57..43cc9a2c2 100644
--- a/R/print.rope.R
+++ b/R/print.rope.R
@@ -28,7 +28,7 @@ print.rope <- function(x, digits = 2, ...) {
 
   # These are the base columns we want to print
   cols <- c(
-    "Parameter", "ROPE_Percentage", "Effects", "Component",
+    attr(x, "grid_cols"), "Parameter", "ROPE_Percentage", "Effects", "Component",
     if (is_multivariate) c("ROPE_low", "ROPE_high")
   )
 
diff --git a/R/rope.R b/R/rope.R
index b16db40d5..c9ba83f41 100644
--- a/R/rope.R
+++ b/R/rope.R
@@ -244,8 +244,8 @@ rope.rvar <- rope.draws
 #' @export
 rope.emmGrid <- function(x, range = "default", ci = 0.95, ci_method = "ETI", verbose = TRUE, ...) {
   xdf <- insight::get_parameters(x)
-
   dat <- rope(xdf, range = range, ci = ci, ci_method = ci_method, verbose = verbose, ...)
+  dat <- .append_datagrid(dat, x)
   attr(dat, "object_name") <- insight::safe_deparse_symbol(substitute(x))
   dat
 }
@@ -253,6 +253,21 @@ rope.emmGrid <- function(x, range = "default", ci = 0.95, ci_method = "ETI", ver
 #' @export
 rope.emm_list <- rope.emmGrid
 
+#' @export
+rope.slopes <- function(x, range = "default", ci = 0.95, ci_method = "ETI", verbose = TRUE, ...) {
+  xrvar <- .get_marginaleffects_draws(x)
+  dat <- rope(xrvar, range = range, ci = ci, ci_method = ci_method, verbose = verbose, ...)
+  dat <- .append_datagrid(dat, x)
+  attr(dat, "object_name") <- insight::safe_deparse_symbol(substitute(x))
+  dat
+}
+
+#' @export
+rope.comparisons <- rope.slopes
+
+#' @export
+rope.predictions <- rope.slopes
+
 
 #' @export
 rope.BFBayesFactor <- function(x, range = "default", ci = 0.95, ci_method = "ETI", verbose = TRUE, ...) {
diff --git a/R/si.R b/R/si.R
index 62ae04a2f..497a60f74 100644
--- a/R/si.R
+++ b/R/si.R
@@ -168,6 +168,7 @@ si.emmGrid <- function(posterior, prior = NULL,
     BF = BF, verbose = verbose, ...
   )
 
+  out <- .append_datagrid(out, posterior)
   attr(out, "ci_method") <- "SI"
   attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(posterior))
   out
@@ -176,6 +177,15 @@ si.emmGrid <- function(posterior, prior = NULL,
 #' @export
 si.emm_list <- si.emmGrid
 
+#' @export
+si.slopes <- si.emmGrid
+
+#' @export
+si.comparisons <- si.emmGrid
+
+#' @export
+si.predictions <- si.emmGrid
+
 
 #' @export
 si.stanfit <- function(posterior, prior = NULL, BF = 1, verbose = TRUE, effects = c("fixed", "random", "all"), ...) {
diff --git a/R/spi.R b/R/spi.R
index 772ac6ba3..1e38c9104 100644
--- a/R/spi.R
+++ b/R/spi.R
@@ -72,6 +72,16 @@ spi.data.frame <- function(x, ci = 0.95, verbose = TRUE, ...) {
   dat
 }
 
+#' @export
+spi.draws <- function(x, ci = 0.95, verbose = TRUE, ...) {
+  dat <- .compute_interval_dataframe(x = .posterior_draws_to_df(x), ci = ci, verbose = verbose, fun = "spi")
+  attr(dat, "object_name") <- insight::safe_deparse_symbol(substitute(x))
+  dat
+}
+
+#' @export
+spi.rvar <- spi.draws
+
 
 #' @export
 spi.MCMCglmm <- function(x, ci = 0.95, verbose = TRUE, ...) {
@@ -130,6 +140,7 @@ spi.sim <- function(x, ci = 0.95, parameters = NULL, verbose = TRUE, ...) {
 spi.emmGrid <- function(x, ci = 0.95, verbose = TRUE, ...) {
   xdf <- insight::get_parameters(x)
   out <- spi(xdf, ci = ci, verbose = verbose, ...)
+  out <- .append_datagrid(out, x)
   attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
   out
 }
@@ -137,6 +148,20 @@ spi.emmGrid <- function(x, ci = 0.95, verbose = TRUE, ...) {
 #' @export
 spi.emm_list <- spi.emmGrid
 
+#' @export
+spi.slopes <- function(x, ci = 0.95, verbose = TRUE, ...) {
+  xrvar <- .get_marginaleffects_draws(x)
+  out <- spi(xrvar, ci = ci, verbose = verbose, ...)
+  out <- .append_datagrid(out, x)
+  attr(out, "object_name") <- insight::safe_deparse_symbol(substitute(x))
+  out
+}
+
+#' @export
+spi.comparisons <- spi.slopes
+
+#' @export
+spi.predictions <- spi.slopes
 
 #' @rdname spi
 #' @export
diff --git a/R/utils.R b/R/utils.R
index be2679b4c..374a04fdc 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -132,7 +132,12 @@
 }
 
 #' @keywords internal
-.is_baysian_emmeans <- function(x) {
+.is_baysian_grid <- function(x) {
+  UseMethod(".is_baysian_grid")
+}
+
+#' @keywords internal
+.is_baysian_grid.emmGrid <- function(x) {
   if (inherits(x, "emm_list")) {
     x <- x[[1]]
   }
@@ -140,6 +145,19 @@
   !(all(dim(post.beta) == 1) && is.na(post.beta))
 }
 
+#' @keywords internal
+.is_baysian_grid.emm_list <- .is_baysian_grid.emmGrid
+
+#' @keywords internal
+.is_baysian_grid.slopes <- function(x) {
+  !is.null(attr(x, "posterior_draws"))
+}
+
+#' @keywords internal
+.is_baysian_grid.predictions <- .is_baysian_grid.slopes
+
+#' @keywords internal
+.is_baysian_grid.comparisons <- .is_baysian_grid.slopes
 
 # safe add cleaned parameter names to a model object
 .add_clean_parameters_attribute <- function(params, model) {
@@ -154,3 +172,32 @@
   attr(params, "clean_parameters") <- cp
   params
 }
+
+#' @keywords internal
+.append_datagrid <- function(results, object) {
+  # results is assumed to be a data frame with "Parameter" column
+  # object is an emmeans / marginalefeects that results is based on
+
+  all_attrs <- attributes(results) # save attributes for later
+
+  grid <- insight::get_datagrid(object)
+  grid_names <- colnames(grid)
+
+  results[colnames(grid)] <- grid
+  results$Parameter <- NULL
+  results <- results[, c(grid_names, setdiff(colnames(results), grid_names)), drop = FALSE]
+
+  # add back attributes
+  most_attrs <- all_attrs[setdiff(names(all_attrs), names(attributes(grid)))]
+  attributes(results)[names(most_attrs)] <- most_attrs
+
+  attr(results, "grid_cols") <- grid_names
+  results
+}
+
+#' @keywords internal
+.get_marginaleffects_draws <- function(object) {
+  # errors and checks are handled by marginaleffects
+  insight::check_if_installed("marginaleffects")
+  data.frame(marginaleffects::posterior_draws(object, shape = "DxP"))
+}
diff --git a/R/utils_bayesfactor.R b/R/utils_bayesfactor.R
index a97ef30e9..1992c63f8 100644
--- a/R/utils_bayesfactor.R
+++ b/R/utils_bayesfactor.R
@@ -179,6 +179,28 @@
   )
 }
 
+.clean_priors_and_posteriors.slopes <- function(posterior, prior,
+                                                verbose = TRUE, ...) {
+  if (is.null(prior)) {
+    prior <- posterior
+    if (verbose) {
+      insight::format_warning("Prior not specified! Please provide the original model to get meaningful results.")
+    }
+  }
+
+  posterior <- .get_marginaleffects_draws(posterior)
+  prior <- .get_marginaleffects_draws(prior)
+
+  list(
+    posterior = posterior,
+    prior = prior
+  )
+}
+
+.clean_priors_and_posteriors.predictions <- .clean_priors_and_posteriors.slopes
+
+.clean_priors_and_posteriors.comparisons <- .clean_priors_and_posteriors.slopes
+
 
 # BMA ---------------------------------------------------------------------
 
diff --git a/man/bayesfactor_parameters.Rd b/man/bayesfactor_parameters.Rd
index f44a6652c..a29ee8d37 100644
--- a/man/bayesfactor_parameters.Rd
+++ b/man/bayesfactor_parameters.Rd
@@ -239,6 +239,9 @@ It is important to provide the correct \code{prior} for meaningful results.
 the priors \emph{only}. See \code{\link[=unupdate]{unupdate()}}.
 \item \strong{Note:} When \code{posterior} is a \code{brmsfit_multiple} model, \code{prior} \strong{must} be provided.
 }
+\item When \code{posterior} is an output from a \code{{marginaleffects}} function, \code{prior} should also be an an output
+from a \code{{marginaleffects}} function equivalent to \code{posterior} but created
+with a model of priors samples \emph{only}.
 \item When \code{posterior} is an \code{emmGrid} / \code{emm_list} object:
 \itemize{
 \item \code{prior} should also be an \code{emmGrid} / \code{emm_list} object equivalent to \code{posterior} but
diff --git a/man/bayesfactor_restricted.Rd b/man/bayesfactor_restricted.Rd
index cf73c6fc8..6ed081598 100644
--- a/man/bayesfactor_restricted.Rd
+++ b/man/bayesfactor_restricted.Rd
@@ -130,6 +130,9 @@ It is important to provide the correct \code{prior} for meaningful results.
 the priors \emph{only}. See \code{\link[=unupdate]{unupdate()}}.
 \item \strong{Note:} When \code{posterior} is a \code{brmsfit_multiple} model, \code{prior} \strong{must} be provided.
 }
+\item When \code{posterior} is an output from a \code{{marginaleffects}} function, \code{prior} should also be an an output
+from a \code{{marginaleffects}} function equivalent to \code{posterior} but created
+with a model of priors samples \emph{only}.
 \item When \code{posterior} is an \code{emmGrid} / \code{emm_list} object:
 \itemize{
 \item \code{prior} should also be an \code{emmGrid} / \code{emm_list} object equivalent to \code{posterior} but
diff --git a/man/bci.Rd b/man/bci.Rd
index a2040bf0a..db4de886b 100644
--- a/man/bci.Rd
+++ b/man/bci.Rd
@@ -9,6 +9,7 @@
 \alias{bci.sim.merMod}
 \alias{bci.sim}
 \alias{bci.emmGrid}
+\alias{bci.slopes}
 \alias{bci.stanreg}
 \alias{bci.brmsfit}
 \alias{bci.BFBayesFactor}
@@ -38,6 +39,8 @@ bcai(x, ...)
 
 \method{bci}{emmGrid}(x, ci = 0.95, verbose = TRUE, ...)
 
+\method{bci}{slopes}(x, ci = 0.95, verbose = TRUE, ...)
+
 \method{bci}{stanreg}(
   x,
   ci = 0.95,
diff --git a/man/p_direction.Rd b/man/p_direction.Rd
index a3b8941f1..f9a2530e7 100644
--- a/man/p_direction.Rd
+++ b/man/p_direction.Rd
@@ -7,6 +7,7 @@
 \alias{p_direction.data.frame}
 \alias{p_direction.MCMCglmm}
 \alias{p_direction.emmGrid}
+\alias{p_direction.slopes}
 \alias{p_direction.stanreg}
 \alias{p_direction.brmsfit}
 \alias{p_direction.BFBayesFactor}
@@ -54,6 +55,15 @@ pd(x, ...)
   ...
 )
 
+\method{p_direction}{slopes}(
+  x,
+  method = "direct",
+  null = 0,
+  as_p = FALSE,
+  remove_na = TRUE,
+  ...
+)
+
 \method{p_direction}{stanreg}(
   x,
   effects = c("fixed", "random", "all"),
diff --git a/man/si.Rd b/man/si.Rd
index c6f769240..45e87e7c3 100644
--- a/man/si.Rd
+++ b/man/si.Rd
@@ -161,6 +161,9 @@ It is important to provide the correct \code{prior} for meaningful results.
 the priors \emph{only}. See \code{\link[=unupdate]{unupdate()}}.
 \item \strong{Note:} When \code{posterior} is a \code{brmsfit_multiple} model, \code{prior} \strong{must} be provided.
 }
+\item When \code{posterior} is an output from a \code{{marginaleffects}} function, \code{prior} should also be an an output
+from a \code{{marginaleffects}} function equivalent to \code{posterior} but created
+with a model of priors samples \emph{only}.
 \item When \code{posterior} is an \code{emmGrid} / \code{emm_list} object:
 \itemize{
 \item \code{prior} should also be an \code{emmGrid} / \code{emm_list} object equivalent to \code{posterior} but
diff --git a/tests/testthat/test-emmGrid.R b/tests/testthat/test-emmGrid.R
index b5fff9968..ed05ad940 100644
--- a/tests/testthat/test-emmGrid.R
+++ b/tests/testthat/test-emmGrid.R
@@ -25,6 +25,7 @@ set.seed(300)
 
 test_that("emmGrid hdi", {
   xhdi <- hdi(all_, ci = 0.95)
+  expect_identical(colnames(xhdi)[1:2], c("group", "contrast"))
   expect_equal(xhdi$CI_low, all_summ$lower.HPD, tolerance = 0.1)
   expect_equal(xhdi$CI_high, all_summ$upper.HPD, tolerance = 0.1)
 
@@ -34,6 +35,7 @@ test_that("emmGrid hdi", {
 
 test_that("emmGrid point_estimate", {
   xpest <- point_estimate(all_, centrality = "all", dispersion = TRUE)
+  expect_identical(colnames(xpest)[1:2], c("group", "contrast"))
   expect_equal(xpest$Median, all_summ$emmean, tolerance = 0.1)
 
   xpest2 <- point_estimate(emc_, centrality = "all", dispersion = TRUE)
@@ -46,56 +48,66 @@ test_that("emmGrid point_estimate", {
 
 test_that("emmGrid ci", {
   xci <- ci(all_, ci = 0.9)
-  expect_equal(length(xci$CI_low), 3)
-  expect_equal(length(xci$CI_high), 3)
+  expect_identical(colnames(xci)[1:2], c("group", "contrast"))
+  expect_length(xci$CI_low, 3)
+  expect_length(xci$CI_high, 3)
 })
 
 test_that("emmGrid eti", {
   xeti <- eti(all_, ci = 0.9)
-  expect_equal(length(xeti$CI_low), 3)
-  expect_equal(length(xeti$CI_high), 3)
+  expect_identical(colnames(xeti)[1:2], c("group", "contrast"))
+  expect_length(xeti$CI_low, 3)
+  expect_length(xeti$CI_high, 3)
 })
 
 test_that("emmGrid equivalence_test", {
   xeqtest <- equivalence_test(all_, ci = 0.9, range = c(-0.1, 0.1))
-  expect_equal(length(xeqtest$ROPE_Percentage), 3)
-  expect_equal(length(xeqtest$ROPE_Equivalence), 3)
+  expect_identical(colnames(xeqtest)[1:2], c("group", "contrast"))
+  expect_length(xeqtest$ROPE_Percentage, 3)
+  expect_length(xeqtest$ROPE_Equivalence, 3)
 })
 
 test_that("emmGrid estimate_density", {
   xestden <- estimate_density(c_, method = "logspline", precision = 5)
-  expect_equal(length(xestden$x), 5)
+  expect_identical(colnames(xestden)[1], "contrast")
+  expect_length(xestden$x, 5)
 })
 
 test_that("emmGrid map_estimate", {
   xmapest <- map_estimate(all_, method = "kernel")
-  expect_equal(length(xmapest$MAP_Estimate), 3)
+  expect_identical(colnames(xmapest)[1:2], c("group", "contrast"))
+  expect_length(xmapest$MAP_Estimate, 3)
 })
 
 
 test_that("emmGrid p_direction", {
   xpd <- p_direction(all_, method = "direct")
-  expect_equal(length(xpd$pd), 3)
+  expect_identical(colnames(xpd)[1:2], c("group", "contrast"))
+  expect_length(xpd$pd, 3)
 })
 
 test_that("emmGrid p_map", {
   xpmap <- p_map(all_, precision = 2^9)
-  expect_equal(length(xpmap$p_MAP), 3)
+  expect_identical(colnames(xpmap)[1:2], c("group", "contrast"))
+  expect_length(xpmap$p_MAP, 3)
 })
 
 test_that("emmGrid p_rope", {
   xprope <- p_rope(all_, range = c(-0.1, 0.1))
-  expect_equal(length(xprope$p_ROPE), 3)
+  expect_identical(colnames(xprope)[1:2], c("group", "contrast"))
+  expect_length(xprope$p_ROPE, 3)
 })
 
 test_that("emmGrid p_significance", {
   xsig <- p_significance(all_, threshold = c(-0.1, 0.1))
-  expect_equal(length(xsig$ps), 3)
+  expect_identical(colnames(xsig)[1:2], c("group", "contrast"))
+  expect_length(xsig$ps, 3)
 })
 
 test_that("emmGrid rope", {
   xrope <- rope(all_, range = "default", ci = 0.9)
-  expect_equal(length(xrope$ROPE_Percentage), 3)
+  expect_identical(colnames(xrope)[1:2], c("group", "contrast"))
+  expect_length(xrope$ROPE_Percentage, 3)
 })
 
 
@@ -107,6 +119,8 @@ test_that("emmGrid describe_posterior", {
     describe_posterior(emc_)$median
   )
 
+  expect_identical(colnames(describe_posterior(all_))[1:2], c("group", "contrast"))
+
   skip_on_cran()
   expect_equal(
     describe_posterior(all_, bf_prior = model_p, test = "bf")$log_BF,
@@ -129,6 +143,7 @@ test_that("emmGrid bayesfactor_parameters", {
   xbfp <- bayesfactor_parameters(all_, prior = model_p, verbose = FALSE)
   xbfp2 <- bayesfactor_parameters(emc_, prior = model_p, verbose = FALSE)
   xbfp3 <- bayesfactor_parameters(emc_, prior = emc_p, verbose = FALSE)
+  expect_identical(colnames(xbfp)[1:2], c("group", "contrast"))
   expect_equal(xbfp$log_BF, xbfp2$log_BF, tolerance = 0.1)
   expect_equal(xbfp$log_BF, xbfp3$log_BF, tolerance = 0.1)
 
@@ -166,6 +181,7 @@ test_that("emmGrid si", {
   set.seed(4)
 
   xrsi <- si(all_, prior = model_p, verbose = FALSE)
+  expect_identical(colnames(xrsi)[1:2], c("group", "contrast"))
   expect_equal(length(xrsi$CI_low), 3)
   expect_equal(length(xrsi$CI_high), 3)
 
diff --git a/tests/testthat/test-marginaleffects.R b/tests/testthat/test-marginaleffects.R
new file mode 100644
index 000000000..11be99559
--- /dev/null
+++ b/tests/testthat/test-marginaleffects.R
@@ -0,0 +1,80 @@
+test_that("emmGrid descrive_posterior", {
+  skip_on_ci()
+  skip_on_cran()
+
+  skip_if_not_installed("rstanarm")
+  skip_if_not_installed("marginaleffects")
+
+  data("mtcars")
+  mtcars$cyl <- factor(mtcars$cyl)
+  mod <- rstanarm::stan_glm(mpg ~ cyl + hp * am, data = mtcars, refresh = 0)
+
+  mfx <- marginaleffects::avg_slopes(mod, by = "am")
+  mfx_samps <- as.data.frame(t(attr(mfx, "posterior_draws")))
+
+  results <- describe_posterior(mfx,
+    centrality = "MAP", ci_method = "hdi",
+    test = c("pd", "rope", "p_map", "equivalence_test")
+  )
+  results_draws <- describe_posterior(mfx_samps,
+    centrality = "MAP", ci_method = "hdi",
+    test = c("pd", "rope", "p_map", "equivalence_test")
+  )
+
+  expect_true(all(c("term", "contrast") %in% colnames(results)))
+  expect_equal(results[setdiff(colnames(results), c("term", "contrast"))],
+    results_draws[setdiff(colnames(results_draws), "Parameter")],
+    ignore_attr = TRUE
+  )
+
+  # estimate_density
+  mfx <- marginaleffects::comparisons(mod,
+    variables = "cyl",
+    newdata = data.frame(hp = 100, am = 0)
+  )
+  samps <- insight::get_parameters(mod)[c("cyl6", "cyl8")]
+
+  res <- estimate_density(mfx)
+  resref <- estimate_density(samps)
+  expect_equal(res[intersect(colnames(res), colnames(resref))],
+    resref[intersect(colnames(res), colnames(resref))],
+    ignore_attr = TRUE
+  )
+})
+
+test_that("emmGrid bayesfactors", {
+  skip_on_ci()
+  skip_on_cran()
+
+  skip_if_not_installed("rstanarm")
+  skip_if_not_installed("marginaleffects")
+
+  data("mtcars")
+  mtcars$cyl <- factor(mtcars$cyl)
+  mod <- rstanarm::stan_glm(mpg ~ cyl + hp * am, data = mtcars, refresh = 0)
+  modp <- unupdate(mod)
+
+  mfx <- marginaleffects::avg_slopes(mod, by = "am")
+  mfxp <- marginaleffects::avg_slopes(modp, by = "am")
+
+  mfx_samps <- as.data.frame(t(attr(mfx, "posterior_draws")))
+  mfxp_samps <- as.data.frame(t(attr(mfxp, "posterior_draws")))
+
+  # SI
+  outsi <- si(mfx, prior = mfxp, verbose = FALSE)
+  outsiref <- si(mfx_samps, prior = mfxp_samps, verbose = FALSE)
+
+  expect_true(all(c("term", "contrast") %in% colnames(outsi)))
+  expect_equal(outsi[setdiff(colnames(outsi), c("term", "contrast"))],
+    outsiref[setdiff(colnames(outsiref), "Parameter")],
+    ignore_attr = TRUE
+  )
+
+  # bayesfactor_parameters
+  bfp <- bayesfactor_parameters(mfx, prior = mfxp, verbose = FALSE)
+  bfpref <- bayesfactor_parameters(mfx_samps, prior = mfxp_samps, verbose = FALSE)
+  expect_equal(bfp[setdiff(colnames(bfp), c("term", "contrast"))],
+    bfpref[setdiff(colnames(bfpref), "Parameter")],
+    ignore_attr = TRUE
+  )
+})