137 MCP Eb4ab38d

Model Context Protocol (MCP) Reference

Protocol Overview

MCP is JSON-RPC 2.0 based protocol for AI-tool integration.

Version: 2025-03-26 Foundation: JSON-RPC 2.0 Architecture: Client-Host-Server

Connection Lifecycle

1. Initialize: Client sends initialize request with capabilities
2. Response: Server responds with its capabilities
3. Handshake: Client sends notifications/initialized
4. Active: Bidirectional messaging
5. Shutdown: Close connections, cleanup

Core Capabilities

Tools (Executable Functions)

Tools are functions that servers expose for execution.

List Tools:

{"method": "tools/list"}

Call Tool:

{
  "method": "tools/call",
  "params": {
    "name": "tool_name",
    "arguments": {}
  }
}

Prompts (Interaction Templates)

Prompts are reusable templates for LLM interactions.

List Prompts:

{"method": "prompts/list"}

Get Prompt:

{
  "method": "prompts/get",
  "params": {
    "name": "prompt_name",
    "arguments": {}
  }
}

Resources (Data Sources)

Resources expose read-only data to clients.

List Resources:

{"method": "resources/list"}

Read Resource:

{
  "method": "resources/read",
  "params": {"uri": "resource://path"}
}

Transport Types

stdio (Local)

Server runs as subprocess. Messages via stdin/stdout.

const transport = new StdioClientTransport({
  command: 'node',
  args: ['server.js']
});

HTTP+SSE (Remote)

POST for requests, GET for server events.

const transport = new StreamableHTTPClientTransport({
  url: 'http://localhost:3000/mcp'
});

Error Codes

• -32700: Parse error
• -32600: Invalid request
• -32601: Method not found
• -32602: Invalid params
• -32603: Internal error
• -32002: Resource not found (MCP-specific)

Best Practices

1. Progressive Disclosure: Load tool definitions on-demand
2. Context Efficiency: Filter data before returning
3. Security: Validate inputs, sanitize outputs
4. Resource Management: Cleanup connections properly
5. Error Handling: Handle all error cases gracefully