MCP Gnu Units

What laszlopere/mcp-gnu-units MCP server does

The laszlopere/mcp-gnu-units MCP server exposes unit conversion and dimensional-analysis operations to AI agents. Its bundled database covers more than 3,000 units across areas such as length, mass, time, temperature, area, volume, energy, power, pressure, speed, and data. It can also work with physical constants and unit prefixes defined by the underlying GNU units data.

Supported operations include converting a value between compatible units, evaluating compound expressions such as kW*h and acre*ft, reducing a quantity to SI base units, searching for units by keyword, retrieving an exact unit definition, listing prefixes, and checking server information through the info health check.

How it works

The project vendors the GNU units database and uses an independent Python conversion engine to interpret its definitions. The bundled source is GNU units 2.27, with definitions.units data version 3.26 dated 2026-02-25. The database is included locally, so conversion requests do not require a network connection or an external conversion service.

Dimensional awareness helps distinguish compatible conversions from invalid ones and supports compound expressions rather than limiting the server to fixed category pairs. Results are deterministic because the same bundled definitions and local engine are used for each request.

Setup and configuration

The distribution name is mcp-gnu-units, and the Python import package is mcp_gnu_units. The project documentation identifies uvx mcp-gnu-units as the intended command, but the README also states that the package has not yet been published to PyPI. As a result, published-package installation may not be available until the remaining release steps are completed.

No environment variables or credentials are documented. The server is designed to use its bundled database rather than a remote API. Attribution, version pins, and checksums for the vendored data are recorded in the repository's NOTICE file.

Tools and capabilities

• convert handles values expressed in one unit and converts them to another.
• convert_to_si reduces quantities to SI base units.
• find_units searches the unit database by keyword.
• define_unit looks up the definition of a unit, prefix, or physical constant.
• list_prefixes exposes the available unit prefixes.
• info provides a health check.

Limitations and notes

The project is marked feature-complete but pre-release. It depends on the definitions included with GNU units 2.27, so its available names and semantics follow that bundled data version. The conversion engine is an independent implementation, while GNU units supplies the database content.

The project and bundled database use GPL-3.0-or-later. The README does not document hosted access, client-specific configuration, authentication, or support for changing the database at runtime.