Agent frameworks and SDKs for building MCP servers
Frameworks and SDKs for building agents in code. Of the 31 tools on our building MCP servers page, 20 fit this narrower job. By pricing: 20 open source. The most-starred open repos here are Pi (116,073 stars), LiteLLM (61,465 stars), OpenAI Agents SDK (Python) (30,023 stars). Most come from the MCP & infra (13), frameworks (5), coding (1) categories.
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Pi
Minimal, extensible open-source terminal coding agent and agent toolkit from Earendil, with a multi-provider LLM API, TypeScript SDK, RPC mode and installable extensions, skills and themes.
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LiteLLM
Open-source AI gateway and Python SDK that calls 100+ LLM providers in the OpenAI format, with cost tracking, guardrails, load balancing and logging.
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OpenAI Agents SDK (Python)
OpenAI's Python SDK for building multi-agent workflows; v0.23.0/0.23.1 released Oct 1-2.
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FastMCP
Pythonic framework for building MCP servers and clients quickly.
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MCP Python SDK
Official Python SDK for building Model Context Protocol servers and clients.
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MCP TypeScript SDK
Official TypeScript SDK for building MCP servers and clients.
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mcp-use
Full-stack MCP framework for building MCP servers, MCP apps and agents that connect to them.
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Claude Agent SDK (Python)
Anthropic's Python SDK for building agents on Claude Code's agent loop, with the CLI bundled, custom tools and hooks.
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Sphere SDK
TypeScript SDK that gives autonomous agents an identity and wallet on the Unicity network to find, negotiate and settle payments with other agents.
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MCP Go SDK
Official Go SDK for building Model Context Protocol servers and clients, maintained with Google.
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MCP C# SDK
Official C# SDK for building MCP servers and clients, maintained with Microsoft.
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MCP Rust SDK
Official Rust SDK for the Model Context Protocol.
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Antigravity SDK
Google's Python SDK for building stateful AI agents powered by Antigravity and Gemini, abstracting the agent loop and runtime.
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MCP Java SDK
Official Java SDK for MCP servers and clients.
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TanStack AI
Type-safe, provider-agnostic TypeScript SDK for chat, tool calling and agents.
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NitroStack
TypeScript framework with decorators and dependency injection for building, testing and deploying MCP servers and MCP apps, with a companion desktop studio.
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Workflow SDK
Vercel's TypeScript SDK for building durable, reliable and observable apps and AI agents.
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Skybridge
Full-stack TypeScript and React framework for building MCP Apps and ChatGPT Apps.
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MCP PHP SDK
Official PHP SDK for building MCP servers and clients, maintained with the PHP Foundation and Symfony.
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Arcade
Actions runtime for enterprise agents with thousands of prebuilt authenticated tools, plus an open-source framework for building your own MCP servers.
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GitHub repos (20)
| Repo | GitHub stars | Licence | Last push |
|---|---|---|---|
| Pi ↗ | 116,073 | MIT | — |
| LiteLLM ↗ | 61,465 | MIT | 2026-10-18 |
| OpenAI Agents SDK (Python) ↗ | 30,023 | MIT | 2026-10-17 |
| FastMCP ↗ | 28,106 | Apache License 2.0 | 2026-10-17 |
| MCP Python SDK ↗ | 24,595 | MIT | 2026-10-17 |
| MCP TypeScript SDK ↗ | 13,595 | MIT, moving to Apache-2.0 for new contributions | 2026-10-13 |
| mcp-use ↗ | 10,772 | MIT | 2026-10-17 |
| Claude Agent SDK (Python) ↗ | 8,293 | — | 2026-10-16 |
| Sphere SDK ↗ | 5,385 | — | 2026-10-17 |
| MCP Go SDK ↗ | 5,240 | — | 2026-10-16 |
| MCP C# SDK ↗ | 4,586 | Apache License 2.0 (moving from MIT; docs under CC BY 4.0) | 2026-10-17 |
| MCP Rust SDK ↗ | 4,023 | Apache License 2.0 (moving from MIT; docs under CC BY 4.0) | 2026-10-17 |
| Antigravity SDK ↗ | 3,768 | — | 2026-10-13 |
| MCP Java SDK ↗ | 3,740 | MIT | 2026-10-16 |
| TanStack AI ↗ | 3,199 | MIT | 2026-10-15 |
Top 15 of 20 by stars. Stars and licence come from each repo, checked when the listing was last verified.
FAQ
What are the best AI tools for building MCP servers focused on agent frameworks and SDKs?
We list 20. The first three by GitHub stars and featured status are Pi: Minimal, extensible open-source terminal coding agent and agent toolkit from Earendil, with a multi-provider LLM API, TypeScript SDK, RPC mode and installable extensions, skills and themes.; LiteLLM: Open-source AI gateway and Python SDK that calls 100+ LLM providers in the OpenAI format, with cost tracking, guardrails, load balancing and logging.; OpenAI Agents SDK (Python): OpenAI's Python SDK for building multi-agent workflows; v0.23.0/0.23.1 released Oct 1-2.
Are there free or open-source options?
Yes: 20 open source. Pricing is as each maker states it.
More from building MCP servers
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