Practical MCP with FastMCP & LangChain

Additional Customization Parameters

The @mcp.tool decorator accepts additional parameters to further customize the tool's behavior:

• output_schema: Define a custom output schema if the return type annotation is not sufficient or if you want to provide more details about the structured output format.

• timeout: Set a custom timeout (in seconds) for the tool's execution, which can help prevent long-running operations from blocking the MCP server. We can, for example, for our tool set a timeout of 30 seconds (development timeouts should be longer to allow for debugging).

• annotations: Add metadata about the tool's behavior.

• And more.

Here's an example of using some of these parameters:

@mcp.tool(
    name="calculate_dog_age",
    description="Calculate the real age of a dog in human years based on the provided dog age.",
    timeout