diff --git a/src/adcp/server/test_controller.py b/src/adcp/server/test_controller.py
index 18c1ce720..9a2c4b535 100644
--- a/src/adcp/server/test_controller.py
+++ b/src/adcp/server/test_controller.py
@@ -683,7 +683,7 @@ async def force_account_status(self, account_id, status):
     from adcp.server.base import ToolContext as _ToolContext
     from adcp.server.serve import RequestMetadata as _RequestMetadata
 
-    async def comply_test_controller(**kwargs: Any) -> str:
+    async def comply_test_controller(**kwargs: Any) -> dict[str, Any]:
         context: _ToolContext | None = None
         if context_factory is not None:
             meta = _RequestMetadata(tool_name="comply_test_controller", transport="mcp")
@@ -693,8 +693,7 @@ async def comply_test_controller(**kwargs: Any) -> str:
                     "context_factory for comply_test_controller returned "
                     f"{type(context).__name__}, not a ToolContext instance"
                 )
-        result = await _handle_test_controller(store, kwargs, context=context)
-        return json.dumps(result)
+        return await _handle_test_controller(store, kwargs, context=context)
 
     tool = Tool.from_function(
         comply_test_controller,
diff --git a/tests/test_test_controller_context.py b/tests/test_test_controller_context.py
index f45ba11f1..616e8468e 100644
--- a/tests/test_test_controller_context.py
+++ b/tests/test_test_controller_context.py
@@ -318,14 +318,11 @@ def build_context(meta: RequestMetadata) -> ToolContext:
     tool = mcp._tool_manager._tools["comply_test_controller"]
     # FastMCP's tool wrapper takes the function args as kwargs.
     fn = tool.fn  # type: ignore[attr-defined]
-    result_json = await fn(
+    result = await fn(
         scenario="force_account_status",
         params={"account_id": "acc-1", "status": "suspended"},
     )
 
-    import json
-
-    result = json.loads(result_json)
     assert result["success"] is True
     assert result["current_state"] == "suspended"
     # The factory ran, built a ToolContext, and the store saw the header-
@@ -340,6 +337,27 @@ def build_context(meta: RequestMetadata) -> ToolContext:
     assert received[0].metadata["tool_name"] == "comply_test_controller"
 
 
+async def test_register_test_controller_list_scenarios_returns_dict():
+    """Regression for #314 — comply_test_controller must return a dict (not a
+    JSON string) through the FastMCP registration path so the JS runner's
+    structuredContent unwrapper can read data.success and data.scenarios."""
+
+    class _Store(TestControllerStore):
+        async def force_account_status(self, account_id: str, status: str) -> dict[str, Any]:
+            return {"previous_state": "active", "current_state": status}
+
+    mcp = create_mcp_server(_MinimalHandler(), name="test-agent")
+    register_test_controller(mcp, _Store())
+
+    tool = mcp._tool_manager._tools["comply_test_controller"]
+    fn = tool.fn  # type: ignore[attr-defined]
+    result = await fn(scenario="list_scenarios")
+
+    assert isinstance(result, dict), "must be a dict, not a JSON string"
+    assert result["success"] is True
+    assert "force_account_status" in result["scenarios"]
+
+
 async def test_register_test_controller_rejects_non_toolcontext_from_factory():
     """Guard rail — a factory that returns a dict instead of a
     ToolContext fails loudly at call time, not deep inside the store."""