diff --git a/stac_fastapi/api/stac_fastapi/api/models.py b/stac_fastapi/api/stac_fastapi/api/models.py
index 1c2146d..eea6c67 100644
--- a/stac_fastapi/api/stac_fastapi/api/models.py
+++ b/stac_fastapi/api/stac_fastapi/api/models.py
@@ -25,6 +25,13 @@ except ImportError:  # pragma: nocover
     from starlette.responses import JSONResponse
 
 
+def _call_post_init(cls, self):
+    """Call __post_init__ from all classes in the MRO that define it."""
+    for base in cls.__mro__:
+        if "__post_init__" in base.__dict__:
+            base.__post_init__(self)
+
+
 def create_request_model(
     model_name="SearchGetRequest",
     base_model: Union[Type[BaseModel], APIRequest] = BaseSearchGetRequest,
@@ -47,7 +54,18 @@ def create_request_model(
 
     # Handle GET requests
     if all([issubclass(m, APIRequest) for m in models]):
-        return make_dataclass(model_name, [], bases=tuple(models))
+        model = make_dataclass(model_name, [], bases=tuple(models))
+
+        # Replace __post_init__ to call all base __post_init methods
+        # since make_dataclass only calls the first one in the MRO
+        def __post_init__(self):
+            for base in model.__mro__:
+                if "__post_init__" in base.__dict__:
+                    base.__post_init__(self)
+
+        model.__post_init__ = __post_init__
+
+        return model
 
     # Handle POST requests
     elif all([issubclass(m, BaseModel) for m in models]):
@@ -97,7 +115,7 @@ class CollectionUri(APIRequest):
 class ItemUri(APIRequest):
     """Get or delete item."""
 
-    collection_id: Annotated[str, Path(description="Collection ID")]
+    collection_id: Annotated[str, Path(description="Item ID")]
     item_id: Annotated[str, Path(description="Item ID")]