Building custom connectors - Claude.ai Documentation (original) (raw)

Getting started

Not sure whether to build an MCP server, a plugin, or both? See what to build.

Key resources

SDK Examples: TypeScript and Python SDKs contain server implementation examples
Protocol Specification: modelcontextprotocol.io
Hosting Solutions: Platforms like Cloudflare offer remote MCP server hosting with autoscaling and OAuth management
Auth Specifications: Review the authorization spec with emphasis on third-party service flows

Transport & authentication

Supported transports

Claude supports both Streamable HTTP and the legacy HTTP+SSE transport. The legacy HTTP+SSE transport is being deprecated in favor of Streamable HTTP.

Authentication features

Supports the 2025-03-26, 2025-06-18, and 2025-11-25 auth specifications
Dynamic Client Registration (DCR) enabled
OAuth callback: https://claude.ai/api/mcp/auth_callback (hosted surfaces); loopback redirect for Claude Code — see callback URLs
Token refresh and expiry support
Custom credentials for non-DCR servers

Protocol features

Supported

Tools, prompts, and resources
Text and image-based tool results
Text and binary resources

Not yet supported

Resource subscriptions
Sampling
Advanced/draft capabilities

Technical specifications

Constraint	Limit
Claude.ai/Desktop max tool result size	~150,000 characters
Claude Code max tool result size	25,000 tokens (configurable via MAX_MCP_OUTPUT_TOKENS)
Claude Code timeout	Configurable via MCP_TOOL_TIMEOUT
Claude.ai/Desktop timeout	300 seconds (5 minutes)
Transport protocol	Streamable HTTP (legacy HTTP+SSE being deprecated)

Testing your server

Add directly to Claude via Settings > Connectors
Use the MCP inspector tool to validate auth flows