google--adk-python/contributing/samples/mcp/mcp_in_agent_tool_stdio

AgentTool with MCP Demo (Stdio Mode)

This demo shows how AgentTool works with MCP (Model Context Protocol) toolsets using stdio mode.

Stdio vs SSE Mode

This demo uses stdio mode where the MCP server runs as a subprocess:

• Simpler setup - No need to start a separate server
• Auto-launched - Server starts automatically when agent runs
• Local process - Uses stdin/stdout for communication

For the SSE (remote server) version, see mcp_in_agent_tool_remote.

Setup

No installation required! The MCP server will be launched automatically using uvx when you run the agent.

The demo uses uvx to fetch and run the MCP simple-tool server directly from the GitHub repository's subdirectory:

uvx --from 'git+https://github.com/modelcontextprotocol/python-sdk.git#subdirectory=examples/servers/simple-tool' \
    mcp-simple-tool

This happens automatically via the stdio connection when the agent starts.

Running the Demo

adk web contributing/samples/mcp

Then select mcp_in_agent_tool_stdio from the list and interact with the agent.

Try These Prompts

The agents do not set a model, so they use the ADK default. Try these prompts:

1. Check available tools:

   What tools do you have access to?
   

2. Fetch and summarize JSON Schema specification:

   Use the mcp_helper to fetch https://json-schema.org/specification and summarize the key features of JSON Schema
   

Architecture

main_agent (root_agent)
  │
  └── AgentTool wrapping:
        │
        └── mcp_helper (sub_agent)
              │
              └── McpToolset (stdio connection)
                    │
                    └── MCP Server (subprocess via uvx)
                          │
                          └── uvx --from git+...#subdirectory=... mcp-simple-tool
                                │
                                └── Website Fetcher Tool

Related

• Issue: #1112 - Using agent as tool outside of adk web doesn't exit cleanly
• Related Issue: #929 - LiteLLM giving error with OpenAI models and Grafana's MCP server
• SSE Version: mcp_in_agent_tool_remote - Uses remote server connection