mcpx-eval

A framework for evaluating open-ended tool use across various large language models.

mcpx-eval can be used to compare the output of different LLMs with the same prompt for a given task using mcp.run tools. This means we're not only interested in the quality of the output, but also curious about the helpfulness of various models when presented with real world tools.

Test configs

The tests/ directory contains pre-defined evals

Installation

uv tool install mcpx-eval

Or from git:

uv tool install git+https://github.com/dylibso/mcpx-eval

Or using uvx without installation:

uvx mcpx-eval

mcp.run Setup

You will need to get an mcp.run session ID by running:

npx --yes -p @dylibso/mcpx gen-session --write

This will generate a new session and write the session ID to a configuration file that can be used by mcpx-eval.

If you need to store the session ID in an environment variable you can run gen-session without the --write flag:

npx --yes -p @dylibso/mcpx gen-session

which should output something like:

Login successful!
Session: kabA7w6qH58H7kKOQ5su4v3bX_CeFn4k.Y4l/s/9dQwkjv9r8t/xZFjsn2fkLzf+tkve89P1vKhQ

Then set the MCP_RUN_SESSION_ID environment variable:

$ export MCP_RUN_SESSION_ID=kabA7w6qH58H7kKOQ5su4v3bX_CeFn4k.Y4l/s/9dQwkjv9r8t/xZFjsn2fkLzf+tkve89P1vKhQ

Usage

Run the my-test test for 10 iterations:

mcpx-eval test --model ... --model ... --config my-test.toml --iter 10

Or run a task directly from mcp.run:

mcpx-eval test --model .. --model .. --task my-task --iter 10

Generate an HTML scoreboard for all evals:

mcpx-eval gen --html results.html --show

Test file

A test file is a TOML file containing the following fields:

• name - name of the test
• task - optional, the name of the mcp.run task to use
• prompt - prompt to test, this is passed to the LLM under test, this can be left blank if task is set
• check - prompt for the judge, this is used to determine the quality of the test output
• expected-tools - list of tool names that might be used
• ignored-tools - optional, list of tools to ignore, they will not be available to the LLM
• import - optional, includes fields from another test TOML file
• vars - optional, a dict of variables that will be used to format the prompt