Arcade MCP is an open-source framework for building Model Context Protocol servers and tools, designed to add custom capabilities to AI agents. It provides a decorator-based API covering the full MCP specification including tools, resources, prompts, and sampling. The framework supports authorized tool calling with OAuth handling and integrates with popular agent frameworks including LangChain, Mastra, Pydantic AI, CrewAI, and OpenAI Agents. It powers over 7,500 prebuilt tools across Arcade.dev and includes CLI tooling for evaluation and deployment.