Supported MCP Methods

mcpr parses every JSON-RPC 2.0 message and classifies it against the MCP specification (2025-03-26). This page lists every supported method, what mcpr does with it, and what fields are logged.

Lifecycle

Method	Proxy Behavior	Logged Fields
initialize	Extracts clientInfo (name, version, platform), tracks session state, captures server metadata and capabilities	session_id, client_name, client_version, client_platform
notifications/initialized	Transitions session to Active state	session_id
ping	Forwarded as-is	—

Tools

Method	Proxy Behavior	Logged Fields
tools/list	CSP rewriting + schema capture with change tracking	mcp_method
tools/call	CSP rewriting, extracts tool name, per-tool metrics	mcp_method, tool, latency_ms, error_code, error_msg
notifications/tools/list_changed	Marks schema as stale	—

Resources

Method	Proxy Behavior	Logged Fields
resources/list	CSP rewriting + schema capture	mcp_method
resources/templates/list	CSP rewriting + schema capture	mcp_method
resources/read	CSP rewriting, extracts resource URI	mcp_method
resources/subscribe	Forwarded as-is	mcp_method
resources/unsubscribe	Forwarded as-is	mcp_method

Prompts

Method	Proxy Behavior	Logged Fields
prompts/list	Schema capture (names, descriptions, arguments)	mcp_method
prompts/get	Extracts prompt name for logging	mcp_method

Utility

Method	Proxy Behavior	Logged Fields
logging/setLevel	Forwarded as-is, classified for logging	mcp_method
completion/complete	Forwarded as-is, classified for logging	mcp_method
notifications/cancelled	Extracts requestId	mcp_method
notifications/progress	Extracts progressToken	mcp_method

Not yet supported

These methods are forwarded as passthrough (not actively classified):

Method	Direction	Notes
sampling/createMessage	Server → Client	Sampling request
roots/list	Server → Client	Root listing request
notifications/resources/list_changed	Server → Client	Resource change notification
notifications/resources/updated	Server → Client	Resource update notification
notifications/prompts/list_changed	Server → Client	Prompt change notification
notifications/roots/list_changed	Client → Server	Root change notification
notifications/message	Server → Client	Log message notification

Unknown methods are forwarded as-is and appear as Unknown in observability output.

Classification

mcpr produces an McpMethod enum value for each recognized method. This value appears in:

• Terminal output (the MCP method column)
• SQLite storage (mcp_method field)
• Cloud sync events
• Event bus ProxyEvent::Request events

The classification happens at the JSON-RPC parsing layer (mcpr-protocol crate) before any routing or CSP logic runs.