unpack tool output

src/langchain_mcp/toolkit.py

@@ -2,6 +2,7 @@
 # SPDX-License-Identifier: MIT
 
 import asyncio
+import json
 import warnings
 from collections.abc import Callable
 
@@ -104,22 +105,27 @@ class MCPTool(BaseTool):
 
     session: ClientSession
     handle_tool_error: bool | str | Callable[[ToolException], str] | None = True
+    response_format: str = "content_and_artifact"
 
     @t.override
-    def _run(self, *args: t.Any, **kwargs: t.Any) -> t.Any:
+    def _run(self, *args: t.Any, **kwargs: t.Any) -> t.Tuple[str, t.Any]:
         warnings.warn(
             "Invoke this tool asynchronousely using `ainvoke`. This method exists only to satisfy standard tests.",
             stacklevel=1,
         )
         return asyncio.run(self._arun(*args, **kwargs))
 
     @t.override
-    async def _arun(self, *args: t.Any, **kwargs: t.Any) -> t.Any:
+    async def _arun(self, *args: t.Any, **kwargs: t.Any) -> t.Tuple[str, t.Any]:
         result = await self.session.call_tool(self.name, arguments=kwargs)
         content = pydantic_core.to_json(result.content).decode()
         if result.isError:
             raise ToolException(content)
-        return content
+        content_blocks = json.loads(content)
+        text_content = "\n".join([block["text"] for block in content_blocks if block["type"] == "text"])
+        artifact = [block["artifact"] for block in content_blocks if "artifact" in block]
+        artifact = None if not artifact else (artifact[0] if len(artifact) == 1 else artifact)
+        return text_content, artifact
 
     @t.override
     @property