New in reflex-enterprise v0.9.4.

Beyond the built-in tools and reflex:// resources, you can register your own tools, resources, and prompts on the underlying server. There are two ways in, and both hand you the same instance.

Pass MCPPlugin(configure=...) a callable (or a "module.function" import path). It is invoked as configure(server) once the built-in tools and resources are registered and before the server is mounted, so whatever you add is serving from the first request:

A tool or resource that declares a Context-typed parameter has it injected by FastMCP, giving you the active request and session — the same mechanism the built-in tools use to resolve the caller's session from their bearer token.

To register from application code instead, grab the active server with rxe.get_mcp_server(). The server is built when the app is compiled, so this has to run after that — a lifespan task is the natural home, since it starts once the backend comes up:

If you register tools after the transport is already serving, connected clients pick them up on their next tools/list.

• Auto MCP: the built-in tools and resources your additions sit alongside.
• Custom MCP resources: the simpler path when all you want is a read-only view of session state.