Practical MCP with FastMCP & LangChain

Requirements and Limitations

There are a few important things to keep in mind about elicitation before we start writing code.

First, elicitation is a client capability. The client must declare during the MCP handshake that it supports elicitation. If a client does not support it, calling ctx.elicit() will raise an error. This means your tool needs to either be designed for clients that support elicitation, or it needs a fallback path for clients that do not.

Second, elicitation requires an active session