MCP Integration

源码版本v2026.7.20

Responsibility

MCP (Model Context Protocol) is a universal protocol for connecting external tools/data sources. Hermes acts both as an MCP client consuming tools exposed by external MCP servers (bridged into ToolRegistry via mcp_tool) and as an MCP server (mcp_serve.py) exposing its own tools to other agent clients. This lets Hermes pull in third-party capabilities without baking them into the core.

Key Files

• tools/mcp_tool.py — MCP client bridge: registers tools from external MCP servers into ToolRegistry
• mcp_serve.py — Hermes as an MCP server exposing its own tools (repo root)
• registry.register:365-436 — MCP-bridged tools go through the same registration path
• register_plugin_override_policy:316-365 — controls namespace admission for MCP/plugin tools
• optional-mcps/ directory — optional MCP server implementations

Data Flow

1. At startup (or via runtime hot reload) MCP config is read and mcp_tool connects to external MCP servers.
2. The list of tools exposed by a server is pulled and each is registered as a ToolEntry via registry.register:365 (namespaced to avoid collisions with built-in tools).
3. Namespace admission is controlled by register_plugin_override_policy:316.
4. The main loop gathers schemas, dispatches tool_calls, and backfills results just as for built-in tools.
5. Reverse direction: Hermes can expose its own tools to other MCP clients via mcp_serve.py, letting editors/other agents call them.

Summary

MCP is Hermes's "capability bus". mcp_tool lets external tools enter the same tool pool as built-ins; mcp_serve.py lets Hermes itself be called by external clients. Everything goes through ToolRegistry, so the main loop does not care whether a tool is built-in or MCP.