mcp.build is a platform of open source MCPs (Model Context Protocol servers) — hosted, ready-to-use tools that make it super easy for AI agents like Claude to interact with real-world services. Copy an endpoint, connect it in a couple of clicks, and start using it from a plain natural-language prompt.
Send emails from natural language prompts.
https://next.hal9.ai/mcp/mcpbuild/send-email
New to MCPs? Learn how to install MCPs.
Machine-readable catalog: agents.json
· Agent instructions: llms.txt
· Want to add one? See contributing on GitHub
Every MCP is already deployed. No servers to run, no infrastructure to manage — just connect and go.
MCPs on this site are built to take plain prompts and turn them into the right tool calls, so agents don't need rigid schemas to get useful work done.
Every MCP is open source and built on the Hal9 agent structure. Anyone can inspect, self-host, or contribute a new one.