fast-agent

You'd use a client which runs locally to coordinate between the LLM/agent and the available tools, similarly to how it's described here https://modelcontextprotocol.io/quickstart/client There are a variety of available clients documented here https://modelcontextprotocol.io/clients If you haven't tried any of these yet, the first place to start is Claude Desktop. If you'd like to write your own agents, consider https://github.com/evalstate/fast-agent EDIT: I may have misunderstood your question. If you're asking "how can I make an API call to OpenAI, and have OpenAI call an MCP server I'm running as part of generating its response to me", the answer is "you can't". You'll want a proxy API that you call which is actually an MCP client, responsible for coordinating between the MCP servers and the OpenAI API upstream agent.