Teknium
c031fec365
MCP tool results carry a server _meta mapping (exposed as .meta by the Python SDK) alongside structuredContent. Servers return namespaced machine-readable contracts there (validated payloads, browser-handoff URLs); Hermes previously dropped the field entirely, so that data was invisible to the agent. Now _meta is included in the JSON tool output, after filtering protocol-reserved keys per the MCP spec's key-name rules: a prefix is reserved when a modelcontextprotocol or mcp label is followed by at least one more label (modelcontextprotocol.io/..., tools.mcp.com/...). Vendor namespaces with a trailing reserved word (com.example.mcp/...) and unprefixed keys pass through. Non-serializable metadata drops the extras rather than failing the call.
218 lines
8.2 KiB
Python
218 lines
8.2 KiB
Python
"""Tests for MCP tool structuredContent preservation."""
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import asyncio
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import json
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from types import SimpleNamespace
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from unittest.mock import AsyncMock, MagicMock, patch
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import pytest
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from tools import mcp_tool
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class _FakeContentBlock:
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"""Minimal content block with .text and .type attributes."""
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def __init__(self, text: str, block_type: str = "text"):
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self.text = text
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self.type = block_type
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class _FakeCallToolResult:
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"""Minimal CallToolResult stand-in.
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Uses camelCase ``structuredContent`` / ``isError`` to match the real
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MCP SDK Pydantic model (``mcp.types.CallToolResult``).
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"""
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def __init__(self, content, is_error=False, structuredContent=None, meta=None):
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self.content = content
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self.isError = is_error
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self.structuredContent = structuredContent
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# Real SDK exposes the wire ``_meta`` field as ``.meta`` (Pydantic alias).
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self.meta = meta
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def _fake_run_on_mcp_loop(coro_or_factory, timeout=30):
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coro = coro_or_factory() if callable(coro_or_factory) else coro_or_factory
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"""Run an MCP coroutine directly in a fresh event loop."""
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loop = asyncio.new_event_loop()
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try:
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# `_rpc_lock` must be created inside the loop that awaits it, or asyncio
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# raises "attached to a different loop". Build it here and attach it to
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# whatever fake server is currently registered under _servers.
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async def _install_lock_and_run():
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for srv in list(mcp_tool._servers.values()):
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if getattr(srv, "_rpc_lock", None) is None:
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srv._rpc_lock = asyncio.Lock()
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return await coro
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return loop.run_until_complete(_install_lock_and_run())
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finally:
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loop.close()
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@pytest.fixture
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def _patch_mcp_server():
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"""Patch _servers and the MCP event loop so _make_tool_handler can run."""
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fake_session = MagicMock()
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# `_rpc_lock` is acquired by _make_tool_handler's call path (mcp_tool.py
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# ~L2008) to serialize JSON-RPC against the server — build it inside the
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# fresh loop that _fake_run_on_mcp_loop spins up, not at fixture import.
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fake_server = SimpleNamespace(session=fake_session, _rpc_lock=None)
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with patch.dict(mcp_tool._servers, {"test-server": fake_server}), \
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patch("tools.mcp_tool._run_on_mcp_loop", side_effect=_fake_run_on_mcp_loop):
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yield fake_session
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class TestStructuredContentPreservation:
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"""Ensure structuredContent from CallToolResult is forwarded."""
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def test_text_only_result(self, _patch_mcp_server):
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"""When no structuredContent, result is text-only (existing behaviour)."""
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session = _patch_mcp_server
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session.call_tool = AsyncMock(
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return_value=_FakeCallToolResult(
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content=[_FakeContentBlock("hello")],
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)
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)
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handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
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raw = handler({})
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data = json.loads(raw)
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assert data == {"result": "hello"}
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def test_structured_content_none_falls_back_to_text(self, _patch_mcp_server):
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"""When structuredContent is explicitly None, fall back to text."""
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session = _patch_mcp_server
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session.call_tool = AsyncMock(
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return_value=_FakeCallToolResult(
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content=[_FakeContentBlock("done")],
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structuredContent=None,
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)
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)
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handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
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raw = handler({})
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data = json.loads(raw)
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assert data == {"result": "done"}
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def test_empty_text_with_structured_content(self, _patch_mcp_server):
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"""When content blocks are empty but structuredContent exists."""
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session = _patch_mcp_server
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payload = {"status": "ok", "data": [1, 2, 3]}
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session.call_tool = AsyncMock(
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return_value=_FakeCallToolResult(
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content=[],
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structuredContent=payload,
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)
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)
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handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
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raw = handler({})
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data = json.loads(raw)
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assert data["result"] == payload
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class TestMetaPassthrough:
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"""Server ``_meta`` is surfaced, minus protocol-reserved keys.
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Ported from MoonshotAI/kimi-code#2596/#2600.
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"""
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def test_vendor_meta_passes_through(self, _patch_mcp_server):
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session = _patch_mcp_server
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session.call_tool = AsyncMock(
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return_value=_FakeCallToolResult(
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content=[_FakeContentBlock("done")],
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meta={"com.example/handoff": {"url": "https://x"}},
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)
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)
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handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
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data = json.loads(handler({}))
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assert data["result"] == "done"
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assert data["_meta"] == {"com.example/handoff": {"url": "https://x"}}
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def test_reserved_meta_keys_dropped(self, _patch_mcp_server):
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session = _patch_mcp_server
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session.call_tool = AsyncMock(
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return_value=_FakeCallToolResult(
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content=[_FakeContentBlock("done")],
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meta={
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"modelcontextprotocol.io/progress": 1,
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"tools.mcp.com/trace": "x",
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"com.example.mcp/vendor": "keep", # trailing mcp label = vendor ns
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"unprefixed": "keep",
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},
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)
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)
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handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
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data = json.loads(handler({}))
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assert data["_meta"] == {
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"com.example.mcp/vendor": "keep",
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"unprefixed": "keep",
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}
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def test_all_reserved_meta_omits_field(self, _patch_mcp_server):
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session = _patch_mcp_server
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session.call_tool = AsyncMock(
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return_value=_FakeCallToolResult(
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content=[_FakeContentBlock("done")],
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meta={"mcp.io/internal": True},
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)
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)
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handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
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data = json.loads(handler({}))
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assert data == {"result": "done"}
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def test_meta_with_structured_content(self, _patch_mcp_server):
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session = _patch_mcp_server
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session.call_tool = AsyncMock(
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return_value=_FakeCallToolResult(
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content=[_FakeContentBlock("txt")],
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structuredContent={"ok": True},
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meta={"com.example/k": "v"},
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)
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)
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handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
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data = json.loads(handler({}))
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assert data == {
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"result": "txt",
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"structuredContent": {"ok": True},
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"_meta": {"com.example/k": "v"},
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}
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def test_non_serializable_meta_dropped(self, _patch_mcp_server):
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session = _patch_mcp_server
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session.call_tool = AsyncMock(
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return_value=_FakeCallToolResult(
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content=[_FakeContentBlock("done")],
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meta={"com.example/obj": object()},
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)
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)
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handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
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data = json.loads(handler({}))
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assert data == {"result": "done"}
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def test_non_dict_meta_ignored(self, _patch_mcp_server):
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session = _patch_mcp_server
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session.call_tool = AsyncMock(
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return_value=_FakeCallToolResult(
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content=[_FakeContentBlock("done")],
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meta="not-a-dict",
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)
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)
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handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
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data = json.loads(handler({}))
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assert data == {"result": "done"}
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class TestReservedMetaKeyPredicate:
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def test_reserved_prefixes(self):
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assert mcp_tool._is_reserved_mcp_meta_key("modelcontextprotocol.io/x")
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assert mcp_tool._is_reserved_mcp_meta_key("mcp.dev/x")
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assert mcp_tool._is_reserved_mcp_meta_key("tools.mcp.com/x")
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def test_vendor_and_unprefixed_not_reserved(self):
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assert not mcp_tool._is_reserved_mcp_meta_key("com.example.mcp/x") # trailing label
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assert not mcp_tool._is_reserved_mcp_meta_key("com.example/x")
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assert not mcp_tool._is_reserved_mcp_meta_key("plain-key")
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assert not mcp_tool._is_reserved_mcp_meta_key("/leading-slash")
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