Practical MCP with FastMCP & LangChain

The Flow of an Elicitation

The elicitation flow involves three parties: the server, the client, and the user.

When a tool decides it needs input, it calls ctx.elicit() with a message and a description of the expected response. The MCP protocol carries that request from the server to the client. The client presents the request to the user — this might be a modal dialog, an inline form, a terminal prompt, or whatever is appropriate for that client's interface. The user responds, and the client sends the response back to the server. The tool then continues executing with the new information.

Server (ctx.elicit) --> Client (show prompt) --> User (responds) --> Client (send response) --> Server (tool continues)