1. Motivation

Autonomous AI coding assistants and agent frameworks (Claude Code, Cursor, Gemini CLI, LangChain) require standardized discovery mechanisms to locate available Model Context Protocol (MCP) servers and tools.

2. Schema Extensions

RFC 0002 introduces the capabilities.interfaces.mcp object into the canonical MSR schema:

"interfaces": {
  "mcp": {
    "version": "2024-11-05",
    "transport": "sse",
    "endpoint": "https://api.example.org/mcp/sse",
    "tools_count": 8,
    "schema_url": "https://api.example.org/mcp/schema.json"
  }
}

3. Transport Protocols

The transport field MUST specify one of:

• "sse": Server-Sent Events over HTTPS for cloud and container hosted servers.
• "stdio": Standard Input/Output streaming for local command-line and desktop tools.
• "streamable-http": Bidirectional chunked HTTP transfer.