Agent, MCP and tool libraries for projects built with AI agents
MCP SDKs and servers, tool calling, agent building blocks. 9 tools ranked by how many of 12,697 public projects built with AI coding agents use them, with downloads and GitHub stars. Updated Oct 10, 2026.
| Tool | Used in agent projects | Downloads / wk | GitHub stars | License |
|---|---|---|---|---|
| Model Context Protocol SDK (JavaScript) npm TypeScript SDK for building MCP servers and clients to extend AI agent capabilities. |
603 (4.7%) | 65.4M | 13.5K | MIT |
| Model Context Protocol SDK (Python) pypi Python SDK for building MCP servers and clients to extend AI agent capabilities. |
484 (3.8%) | 60.6M | 24.5K | MIT |
| FastMCP (Python) pypi Fast, Pythonic framework for building MCP servers and clients for AI tool integration. |
169 (1.3%) | 14.3M | 28K | — |
| LangChain (Python) pypi Framework for composing applications with LLMs through chains and agents. |
141 (1.1%) | 37.3M | 148K | MIT |
| LangGraph pypi Framework for building stateful, multi-actor applications with LLMs. |
82 (0.6%) | 12.1M | 43K | — |
| LangChain.js npm Build applications with LLMs using composable abstractions for chains, agents and memory. |
67 (0.5%) | 6.2M | 18.3K | MIT |
| Mastra npm Framework for building AI agents with tools, memory and MCP server support. |
39 (0.3%) | 2M | 28.7K | Apache-2.0 |
| fastMCP (JavaScript) npm TypeScript framework for building Model Context Protocol servers. |
33 (0.3%) | 709K | 3,274 | MIT |
| LangChain (JavaScript) npm TypeScript framework for building applications with LLMs, chains, agents and memory. |
30 (0.2%) | 3.1M | 18.3K | MIT |
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