diff --git a/openfisca_core/tracers/flat_trace.py b/openfisca_core/tracers/flat_trace.py
index aea9288e3..412ac8b02 100644
--- a/openfisca_core/tracers/flat_trace.py
+++ b/openfisca_core/tracers/flat_trace.py
@@ -37,27 +37,6 @@ def get_serialized_trace(self) -> t.SerializedNodeMap:
             for key, flat_trace in self.get_trace().items()
         }
 
-    def serialize(
-        self,
-        value: None | t.VarArray | t.ArrayLike[object],
-    ) -> None | t.ArrayLike[object]:
-        if value is None:
-            return None
-
-        if isinstance(value, EnumArray):
-            return value.decode_to_str().tolist()
-
-        if isinstance(value, numpy.ndarray) and numpy.issubdtype(
-            value.dtype,
-            numpy.dtype(bytes),
-        ):
-            return value.astype(numpy.dtype(str)).tolist()
-
-        if isinstance(value, numpy.ndarray):
-            return value.tolist()
-
-        return value
-
     def _get_flat_trace(
         self,
         node: t.TraceNode,
@@ -83,3 +62,27 @@ def key(node: t.TraceNode) -> t.NodeKey:
         name = node.name
         period = node.period
         return t.NodeKey(f"{name}<{period}>")
+
+    @staticmethod
+    def serialize(
+        value: None | t.VarArray | t.ArrayLike[object],
+    ) -> None | t.ArrayLike[object]:
+        if value is None:
+            return None
+
+        if isinstance(value, EnumArray):
+            return value.decode_to_str().tolist()
+
+        if isinstance(value, numpy.ndarray) and numpy.issubdtype(
+            value.dtype,
+            numpy.dtype(bytes),
+        ):
+            return value.astype(numpy.dtype(str)).tolist()
+
+        if isinstance(value, numpy.ndarray):
+            return value.tolist()
+
+        return value
+
+
+__all__ = ["FlatTrace"]
diff --git a/openfisca_core/tracers/full_tracer.py b/openfisca_core/tracers/full_tracer.py
index 56109cc9f..f6f793e19 100644
--- a/openfisca_core/tracers/full_tracer.py
+++ b/openfisca_core/tracers/full_tracer.py
@@ -91,10 +91,10 @@ def generate_performance_tables(self, dir_path: str) -> None:
     def get_nb_requests(self, variable: str) -> int:
         return sum(self._get_nb_requests(tree, variable) for tree in self.trees)
 
-    def get_flat_trace(self) -> dict:
+    def get_flat_trace(self) -> t.FlatNodeMap:
         return self.flat_trace.get_trace()
 
-    def get_serialized_flat_trace(self) -> dict:
+    def get_serialized_flat_trace(self) -> t.SerializedNodeMap:
         return self.flat_trace.get_serialized_trace()
 
     def browse_trace(self) -> Iterator[t.TraceNode]:
@@ -161,3 +161,6 @@ def _get_nb_requests(self, tree: t.TraceNode, variable: str) -> int:
     @staticmethod
     def _get_time_in_sec() -> t.Time:
         return time.time_ns() / (10**9)
+
+
+__all__ = ["FullTracer"]
diff --git a/openfisca_core/tracers/types.py b/openfisca_core/tracers/types.py
new file mode 100644
index 000000000..f26c85424
--- /dev/null
+++ b/openfisca_core/tracers/types.py
@@ -0,0 +1,108 @@
+from __future__ import annotations
+
+from collections.abc import Iterator
+from typing import NewType, Protocol
+from typing_extensions import TypeAlias, TypedDict
+
+from openfisca_core.types import (
+    Array,
+    ArrayLike,
+    ParameterNode,
+    ParameterNodeChild,
+    Period,
+    PeriodInt,
+    VariableName,
+)
+
+from numpy import generic as VarDType
+
+#: A type of a generic array.
+VarArray: TypeAlias = Array[VarDType]
+
+#: A type representing a unit time.
+Time: TypeAlias = float
+
+#: A type representing a mapping of flat traces.
+FlatNodeMap: TypeAlias = dict["NodeKey", "FlatTraceMap"]
+
+#: A type representing a mapping of serialized traces.
+SerializedNodeMap: TypeAlias = dict["NodeKey", "SerializedTraceMap"]
+
+#: A stack of simple traces.
+SimpleStack: TypeAlias = list["SimpleTraceMap"]
+
+#: Key of a trace.
+NodeKey = NewType("NodeKey", str)
+
+
+class FlatTraceMap(TypedDict, total=True):
+    dependencies: list[NodeKey]
+    parameters: dict[NodeKey, None | ArrayLike[object]]
+    value: None | VarArray
+    calculation_time: Time
+    formula_time: Time
+
+
+class SerializedTraceMap(TypedDict, total=True):
+    dependencies: list[NodeKey]
+    parameters: dict[NodeKey, None | ArrayLike[object]]
+    value: None | ArrayLike[object]
+    calculation_time: Time
+    formula_time: Time
+
+
+class SimpleTraceMap(TypedDict, total=True):
+    name: VariableName
+    period: int | Period
+
+
+class ComputationLog(Protocol):
+    def print_log(self, aggregate: bool = ..., max_depth: int = ..., /) -> None: ...
+
+
+class FlatTrace(Protocol):
+    def get_trace(self, /) -> FlatNodeMap: ...
+    def get_serialized_trace(self, /) -> SerializedNodeMap: ...
+
+
+class FullTracer(Protocol):
+    @property
+    def trees(self, /) -> list[TraceNode]: ...
+    def browse_trace(self, /) -> Iterator[TraceNode]: ...
+
+
+class PerformanceLog(Protocol):
+    def generate_graph(self, dir_path: str, /) -> None: ...
+    def generate_performance_tables(self, dir_path: str, /) -> None: ...
+
+
+class SimpleTracer(Protocol):
+    @property
+    def stack(self, /) -> SimpleStack: ...
+    def record_calculation_start(
+        self, variable: VariableName, period: PeriodInt | Period, /
+    ) -> None: ...
+    def record_calculation_end(self, /) -> None: ...
+
+
+class TraceNode(Protocol):
+    children: list[TraceNode]
+    end: Time
+    name: str
+    parameters: list[TraceNode]
+    parent: None | TraceNode
+    period: PeriodInt | Period
+    start: Time
+    value: None | VarArray
+
+    def calculation_time(self, *, round_: bool = ...) -> Time: ...
+    def formula_time(self, /) -> Time: ...
+    def append_child(self, node: TraceNode, /) -> None: ...
+
+
+__all__ = [
+    "ArrayLike",
+    "ParameterNode",
+    "ParameterNodeChild",
+    "PeriodInt",
+]
diff --git a/openfisca_core/types.py b/openfisca_core/types.py
index 9fb94d1f5..9c8105741 100644
--- a/openfisca_core/types.py
+++ b/openfisca_core/types.py
@@ -148,8 +148,31 @@ class MemoryUsage(TypedDict, total=False):
 
 # Parameters
 
+#: A type representing a node of parameters.
+ParameterNode: TypeAlias = Union[
+    "ParameterNodeAtInstant", "VectorialParameterNodeAtInstant"
+]
 
-class ParameterNodeAtInstant(Protocol): ...
+#: A type representing a ???
+ParameterNodeChild: TypeAlias = Union[ParameterNode, ArrayLike[object]]
+
+
+class ParameterNodeAtInstant(Protocol):
+    _instant_str: InstantStr
+
+    def __contains__(self, __item: object, /) -> bool: ...
+    def __getitem__(
+        self, __index: str | Array[DTypeGeneric], /
+    ) -> ParameterNodeChild: ...
+
+
+class VectorialParameterNodeAtInstant(Protocol):
+    _instant_str: InstantStr
+
+    def __contains__(self, item: object, /) -> bool: ...
+    def __getitem__(
+        self, __index: str | Array[DTypeGeneric], /
+    ) -> ParameterNodeChild: ...
 
 
 # Periods