MCP (Model Context Protocol) Writer

The MCP Writer is a key component of FME's MCP (Model Context Protocol) integration.

The writer is used to define a tool response that will be returned when the workspace is run as an MCP tool in FME Flow. This will allow users to take any data processed in an FME workspace and shape it into an MCP tool response that an MCP client (for example, AI agents) can consume directly.

Product and System Requirements

Format

FME Platform

Operating System

Reader/Writer

FME Form

FME Flow

FME Flow Hosted

Windows 64-bit

Linux

Mac

Writer

Yes

Yes

Yes

Yes

Yes

Yes

Writer Overview

When a workspace containing the MCP Writer is run, the writer accumulates all features routed to it and serializes them into a JSON-RPC 2.0 formatted response document.

The resulting JSON document will then be used by FME Flow to return an MCP Response. The output file conforms to the tool response format and requirements defined in the MCP Tools Specification.

Note  After FME Flow's MCP Server sends the tool result to the MCP Client, the AI agent is responsible for interpreting the data. Different AI agents may interpret the same result in different ways.

Authoring a Workspace

Adding an MCP Writer

Some user parameter types are not supported by MCP. Selecting the MCP format in the Add Writer or Generate Workspace dialogs displays an information banner about validating parameter types to ensure MCP compatibility.

To open the User Parameter Manager from the Navigator:

  • Right-click on the User Parameters icon, and select Manage User Parameters

  • From the Workbench menu, select Build > Manage User Parameters.

For more information, see User Parameter Properties.

Populating the Writer Dataset

How to populate the FME Form Writer Dataset.

Resources