List all metrics from the MetricFlow project.

If the user is asking a data-related or business-related question,
this tool should be used as a first step to get a list of metrics
that can be used with other tools to answer the question.

This tool executes the `mf list metrics --json` command locally
and returns the metric definitions in JSON format.

Examples:
- "What metrics are available in our project?"
- "Show me all revenue-related metrics"
- "What are the key performance indicators we track?"

The output includes metric names, descriptions, types, and expressions
that can be used to understand what data is available for analysis. 