FME Transformers: 2026.1

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Categories
Integrations

Integrations

Related Transformers
AzureBlobStorageConnector
AzureFileStorageConnector
BoxConnector
CesiumIonConnector
ComprehendConnector
DropboxConnector
GoogleCloudStorageConnector
GoogleDriveConnector
HDFSConnector
OneDriveConnector
RekognitionConnector
SQSConnector

MCPCaller

Connects to an MCP (Model Context Protocol) server to list and call tools.

Note  This transformer is in Tech Preview. Updates to this package during Tech Preview may not be backwards compatible.

Jump to Configuration

Typical Uses

  • Access data from remote services using MCP tool calls
  • Perform operations against remote services using MCP tool calls
  • Integrate MCP-based workflows into FME workflows

How does it work?

The MCPCaller is a Model Context Protocol (MCP) client that uses your credentials to perform various tasks:

MCP Method Task

List Tools

List the available tools on the MCP server.

Call Tool

Call a tool on the MCP server.

It supports MCP servers that use the Streamable HTTP transport.

Optional Input Port

This transformer has two modes, depending on whether a connector is attached to the Input port or not:

  • Input-driven: When input features are connected, the transformer runs once for each feature it receives in the Input port.
  • Run Once: When no input features are connected, the transformer runs one time.

When the Input port is in use, the Initiator output port is also enabled.

Usage Notes

  • Requires FME 2026.1+ and Python 3.12, 3.13, or 3.14.

Configuration

Input Ports

This transformer accepts any feature.

Output Ports

Features with added attributes, as specified in parameters and according to MCP Method:

MCP Method

Output - Input-Driven

Output - Run Once

List Tools

Multiple features, one for each available tool, with details about the tool.

Multiple new features, one for each available tool, with details about the tool.

Call Tool

Input feature with results of the tool call.

New feature with results of the tool call.

On successful connection to the MCP server, one feature is output here, with these metadata attributes:

_name

Name of the server.

_version

Version of the server.

_protocolVersion

MCP protocol version of the server.

_instructions

Usage instructions provided by the server, if any.

_capabilities

JSON of the server's declared capabilities.

_mcp_response

Added when Include Response JSON is Yes. Contains the complete JSON response.

When the optional Input port is used, input features are output here unmodified, in addition to any other output locations (Output or <Rejected>).

Features that cause the operation to fail are output through this port. An fme_rejection_code attribute describing the category of the error will be added, along with a more descriptive fme_rejection_message which contains more specific details as to the reason for the failure.

If an Input feature already has a value for fme_rejection_code, this value will be removed.

Rejected Feature Handling: can be set to either terminate the translation or continue running when it encounters a rejected feature. This setting is available both as a default FME option and as a workspace parameter.

Parameters

Credential Source

Select the type of credentials to use:

  • None: Use an MCP server without authentication.
  • Web Connection: Use a connection that defines an MCP server URL and bearer token, or an OAuth 2.0 MCP credential.

Account

When Credential Source is Web Connection, select or create a Web Connection connecting to an appropriate Web Service.

See Using Web Connections.

MCP Server URL

 

When Credential Source is None, provide the URL of the MCP server to connect to.

The server must support the Streamable HTTP transport.

Override Server

(Optional) When Credential Source is Web Connection, enable this to override the URL specified in the web connection.

MCP Server URL

Provide an MCP server URL. Must support the Streamable HTTP transport.

MCP Method

Select an operation to perform. Choices include:

  • List Tools
  • Call Tool

This method has no additional parameters.

Added Attributes

Output features will receive these attributes:

_name

The unique identifier for the tool.

_title

User-friendly title for the tool. Null if not available.

_description

A description of what the tool does. Null if not available.

_inputSchema

JSON Schema defining the expected input parameters for the tool.

_outputSchema

JSON Schema defining the structure of the tool's output. Null if not available.

_annotations

JSON containing optional metadata for the tool. Null if not available.

_icons{}

List attribute of icons for the tool. Null if not available.

_icons{}.src

Image data in base64-encoded format.

_icons{}.mimeType

Media type of the image (e.g. image/png).

_icons{}.sizes{}

List of sizes available for the icon (e.g. "64x64", "128x128").

_mcp_response

Added when Include Response JSON is Yes. Contains the complete JSON response.

Tools

Tool Name

Specify the tool to call.

Input Schema

After providing a Tool Name, the input schema will be populated here.

Tool Input

Tool input must be JSON and conform to the input schema defined by the tool.

JSON Input

Select the JSON input source type:

  • Text or Attribute: Read the JSON input from the JSON Text parameter.
  • File: Read the JSON input from a file specified in the JSON File parameter.

JSON Text

When JSON Input is Text or Attribute, provide the input, which may be entered directly or provided as an attribute or parameter value.

Note that once a Tool Name has been specified, this parameter is populated with a template based on the tool's Input Schema.

JSON File

When JSON Input is File, provide the path to a file containing the JSON input.

Advanced

Include Response JSON

Select an option:

  • No (default): Do nothing.
  • Yes: An _mcp_response attribute is added to Output and Server Information output features, containing the raw JSON of the MCP response for that operation. This may be useful for inspecting the full server response or accessing fields not otherwise exposed as attributes.

Added Attributes

Output features will receive these attributes:

_data

JSON data returned by the tool, if applicable.

_content{}

List attribute where each element is a type of content returned by the tool call.

_content{}.type

Value indicating the type of content: "text", "image", "audio", "resource", "resource_link".

_content{}.text

Text content. Only applicable to the text content type.

_content{}.data

Binary content data in base64-encoded format. Only applicable to image and audio content types.

_content{}.mimeType

Data's media type. Only applicable to image and audio content types.

_content{}.annotations

JSON containing optional metadata for the content. Null if not available.

_mcp_response

Added when Include Response JSON is Yes. Contains the complete JSON response.

Editing Transformer Parameters

Transformer parameters can be set by directly entering values, using expressions, or referencing other elements in the workspace such as attribute values or user parameters. Various editors and context menus are available to assist. To see what is available, click beside the applicable parameter.

Defining Values

There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters.

Using the Text Editor

The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.

Text Editor

Using the Arithmetic Editor

The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.

Arithmetic Editor

Conditional Values

Set values depending on one or more test conditions that either pass or fail.

Parameter Condition Definition Dialog

Content

Expressions and strings can include a number of functions, characters, parameters, and more.

When setting values - whether entered directly in a parameter or constructed using one of the editors - strings and expressions containing String, Math, Date/Time or FME Feature Functions will have those functions evaluated. Therefore, the names of these functions (in the form @<function_name>) should not be used as literal string values.

String Functions

These functions manipulate and format strings.

Special Characters

 A set of control characters is available in the Text Editor.

Math Functions

Math functions are available in both editors.
Date/Time Functions Date and time functions are available in the Text Editor.

Math Operators

These operators are available in the Arithmetic Editor.

FME Feature Functions

These return primarily feature-specific values.

FME Parameters

FME and workspace-specific parameters may be used.
Creating and Modifying User Parameters Create your own editable parameters.

Table Tools

Transformers with table-style parameters have additional tools for populating and manipulating values.

Row Reordering

Enabled once you have clicked on a row item. Choices include:

  • Add a row
  • Remove a row
  • Move current row up one
  • Move current row down one
  • Move current row to top
  • Move current row to bottom

Cut, Copy, and Paste

Enabled once you have clicked on a row item. Choices include:

  • Cut a row - delete and copy to clipboard
  • Copy a row to the clipboard
  • Paste a row from the clipboard

Cut, copy, and paste may be used within a transformer, or between transformers.

Filter

Start typing a string, and the matrix will only display rows matching those characters. Searches all columns. This only affects the display of attributes within the transformer - it does not alter which attributes are output.

Import

Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers.

Reset/Refresh

Generally resets the table to its initial state, and may provide additional options to remove invalid entries. Behavior varies between transformers.

Note: Not all tools are available in all transformers.

For more information, see Transformer Parameter Menu Options.

Reference

Processing Behavior

Feature-Based

Feature Holding

No
Dependencies  
Aliases  
History  

FME Online Resources

The FME Community and Support Center Knowledge Base have a wealth of information, including active forums with 35,000+ members and thousands of articles.

Search for all results about the MCPCaller on the FME Community.

 

Examples may contain information licensed under the Open Government Licence – Vancouver, Open Government Licence - British Columbia, and/or Open Government Licence – Canada.