131 lines
5.2 KiB
Python
131 lines
5.2 KiB
Python
"""MCP client: connects to MCP servers and wraps their tools as native nanobot tools."""
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import asyncio
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from contextlib import AsyncExitStack
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from typing import Any
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import httpx
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from loguru import logger
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from nanobot.agent.tools.base import Tool
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from nanobot.agent.tools.registry import ToolRegistry
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class MCPToolWrapper(Tool):
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"""Wraps a single MCP server tool as a nanobot Tool."""
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def __init__(self, session, server_name: str, tool_def, tool_timeout: int = 30):
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self._session = session
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self._original_name = tool_def.name
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self._name = f"mcp_{server_name}_{tool_def.name}"
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self._description = tool_def.description or tool_def.name
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self._parameters = tool_def.inputSchema or {"type": "object", "properties": {}}
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self._tool_timeout = tool_timeout
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@property
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def name(self) -> str:
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return self._name
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@property
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def description(self) -> str:
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return self._description
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@property
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def parameters(self) -> dict[str, Any]:
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return self._parameters
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async def execute(self, **kwargs: Any) -> str:
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from mcp import types
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try:
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result = await asyncio.wait_for(
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self._session.call_tool(self._original_name, arguments=kwargs),
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timeout=self._tool_timeout,
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)
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except asyncio.TimeoutError:
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logger.warning("MCP tool '{}' timed out after {}s", self._name, self._tool_timeout)
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return f"(MCP tool call timed out after {self._tool_timeout}s)"
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parts = []
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for block in result.content:
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if isinstance(block, types.TextContent):
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parts.append(block.text)
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else:
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parts.append(str(block))
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return "\n".join(parts) or "(no output)"
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async def connect_mcp_servers(
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mcp_servers: dict, registry: ToolRegistry, stack: AsyncExitStack
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) -> None:
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"""Connect to configured MCP servers and register their tools."""
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from mcp import ClientSession, StdioServerParameters
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from mcp.client.sse import sse_client
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from mcp.client.stdio import stdio_client
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from mcp.client.streamable_http import streamable_http_client
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for name, cfg in mcp_servers.items():
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try:
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transport_type = cfg.type
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if not transport_type:
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if cfg.command:
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transport_type = "stdio"
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elif cfg.url:
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# Convention: URLs ending with /sse use SSE transport; others use streamableHttp
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transport_type = (
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"sse" if cfg.url.rstrip("/").endswith("/sse") else "streamableHttp"
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)
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else:
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logger.warning("MCP server '{}': no command or url configured, skipping", name)
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continue
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if transport_type == "stdio":
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params = StdioServerParameters(
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command=cfg.command, args=cfg.args, env=cfg.env or None
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)
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read, write = await stack.enter_async_context(stdio_client(params))
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elif transport_type == "sse":
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def httpx_client_factory(
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headers: dict[str, str] | None = None,
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timeout: httpx.Timeout | None = None,
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auth: httpx.Auth | None = None,
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) -> httpx.AsyncClient:
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merged_headers = {**(cfg.headers or {}), **(headers or {})}
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return httpx.AsyncClient(
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headers=merged_headers or None,
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follow_redirects=True,
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timeout=timeout,
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auth=auth,
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)
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read, write = await stack.enter_async_context(
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sse_client(cfg.url, httpx_client_factory=httpx_client_factory)
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)
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elif transport_type == "streamableHttp":
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# Always provide an explicit httpx client so MCP HTTP transport does not
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# inherit httpx's default 5s timeout and preempt the higher-level tool timeout.
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http_client = await stack.enter_async_context(
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httpx.AsyncClient(
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headers=cfg.headers or None,
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follow_redirects=True,
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timeout=None,
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)
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)
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read, write, _ = await stack.enter_async_context(
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streamable_http_client(cfg.url, http_client=http_client)
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)
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else:
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logger.warning("MCP server '{}': unknown transport type '{}'", name, transport_type)
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continue
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session = await stack.enter_async_context(ClientSession(read, write))
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await session.initialize()
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tools = await session.list_tools()
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for tool_def in tools.tools:
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wrapper = MCPToolWrapper(session, name, tool_def, tool_timeout=cfg.tool_timeout)
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registry.register(wrapper)
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logger.debug("MCP: registered tool '{}' from server '{}'", wrapper.name, name)
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logger.info("MCP server '{}': connected, {} tools registered", name, len(tools.tools))
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except Exception as e:
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logger.error("MCP server '{}': failed to connect: {}", name, e)
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