diff --git a/framework/conformance.py b/framework/conformance.py
index df5a4bf..d3e71ac 100644
--- a/framework/conformance.py
+++ b/framework/conformance.py
@@ -15,6 +15,30 @@ from api.od import ODAPI, bind_api_readonly
 import functools
 
 
+def eval_context_decorator(func):
+    """
+    Used to mark functions that can be called inside the evaluation context.
+    Base functions are mapped into the function, as well as the evaluation context.
+    This happens at runtime so typechecking will not be happy.
+    Important: Using the same name in the evaluation context as the function name
+    will lead to naming conflicts with the function as priority, resulting in missing argument errors.
+
+        from typing import TYPE_CHECKING
+        if TYPE_CHECKING:
+            from api.od_stub import *
+            ...
+
+    Use this to make partially fix the typechecking.
+    Optionally, define a stub for your own evaluation context and include it.
+    """
+    def wrapper(*args, api_context, eval_context, **kwargs):
+        for key, value in api_context.items():
+            func.__globals__[key] = value
+        for key, value in eval_context.items():
+            func.__globals__[key] = value
+        return func(*args, **kwargs)
+    return wrapper
+
 def render_conformance_check_result(error_list):
     if len(error_list) == 0:
         return "CONFORM"
@@ -25,7 +49,7 @@ def render_conformance_check_result(error_list):
 
 class Conformance:
     # Parameter 'constraint_check_subtypes': whether to check local type-level constraints also on subtypes.
-    def __init__(self, state: State, model: UUID, type_model: UUID, constraint_check_subtypes=True):
+    def __init__(self, state: State, model: UUID, type_model: UUID, constraint_check_subtypes=True, *, eval_context = None):
         self.state = state
         self.bottom = Bottom(state)
         self.model = model
@@ -51,6 +75,9 @@ class Conformance:
         self.structures = {}
         self.candidates = {}
 
+        # add user defined functions to constraints
+        self.eval_context = eval_context if eval_context else {}
+
 
     def check_nominal(self, *, log=False):
         """
@@ -248,6 +275,13 @@ class Conformance:
                 raise Exception(f"{description} evaluation result should be boolean or string! Instead got {result}")
 
         # local constraints
+        _api_context = bind_api_readonly(self.odapi)
+        _global_binds = {**_api_context}
+        _eval_context = {**self.eval_context}
+        for key, code in _eval_context.items():
+            _f = functools.partial(code, **{"api_context" :_api_context, "eval_context":_eval_context})
+            _global_binds[key] = _f
+            _eval_context[key] = _f
         for type_name in self.bottom.read_keys(self.type_model):
             code = get_code(type_name)
             if code != None:
@@ -256,7 +290,7 @@ class Conformance:
                     description = f"Local constraint of \"{type_name}\" in \"{obj_name}\""
                     # print(description)
                     try:
-                        result = exec_then_eval(code, _globals=bind_api_readonly(self.odapi), _locals={'this': obj_id}) # may raise
+                        result = exec_then_eval(code, _globals=_global_binds, _locals={'this': obj_id}) # may raise
                         check_result(result, description)
                     except:
                         errors.append(f"Runtime error during evaluation of {description}:\n{indent(traceback.format_exc(), 6)}")
@@ -278,7 +312,7 @@ class Conformance:
             if code != None:
                 description = f"Global constraint \"{tm_name}\""
                 try:
-                    result = exec_then_eval(code, _globals=bind_api_readonly(self.odapi)) # may raise
+                    result = exec_then_eval(code, _globals=_global_binds) # may raise
                     check_result(result, description)
                 except:
                     errors.append(f"Runtime error during evaluation of {description}:\n{indent(traceback.format_exc(), 6)}")