diff --git a/README.md b/README.md
index da2b3ef..42b9bca 100644
--- a/README.md
+++ b/README.md
@@ -7,9 +7,10 @@ SPDX-License-Identifier: GPL-3.0-or-later
 [![REUSE status](https://api.reuse.software/badge/github.com/bofh69/nfc2klipper)](https://api.reuse.software/info/github.com/bofh69/nfc2klipper)
 ![GitHub Workflow Status](https://github.com/bofh69/nfc2klipper/actions/workflows/pylint.yml/badge.svg)
 
+
 # nfc2klipper
 
-Set loaded spool & filament in klipper from NFC tags.
+Set loaded spool & filament in klipper from NFC/RFID tags.
 
 
 ## Preparing an NFC reader
@@ -29,20 +30,32 @@ for how to configure a raspberry pi for it.
 
 ## Preparing klipper
 
-Klipper should have two gcode macros:
+When a tag has been read, it will send these gcodes to Klipper:
+
+* SET_ACTIVE_FILAMENT ID=n1
+* SET_ACTIVE_SPOOL ID=n2
+
+
+See [klipper-spoolman.cfg] for the klipper config for them.
+
+
+## Preparing the slicer
+
+For every filament, add a custom start gcode that calls:
+
+`ASSERT_ACTIVE_FILAMENT ID=<id>`
 
-* SET_ACTIVE_FILAMENT ID=n
-* SET_ACTIVE_SPOOL ID=n
+where `<id>` is its filament id in Spoolman.
 
+This can be done automatically by using [sm2ss](https://github.com/bofh69/sm2ss).
 
-See [klipper-spoolman.cfg] for klipper config for them.
 
 ## Preparing tags
 
 The tags should contain an NDEF record with a text block like this:
 ```
-SPOOL: 3
-FILAMENT: 2
+SPOOL:3
+FILAMENT:2
 ```
 
 The numbers are the id numbers that will be sent to the macros in
@@ -51,5 +64,5 @@ klipper via the [Moonraker](https://github.com/Arksine/moonraker) API.
 
 This can be written via NXP's TagWriter on a phone, or better yet,
 use the `write_tags.py` program. The later fetches Spoolman's filaments,
-shows a simple GUI, press return on the chosen spool and it will be
-written to the tag.
+shows a simple text interface where the spool can be chosen, then press
+return to write to the tag.