MCP server

Language models are unreliable at unit arithmetic. The UnifyUnits MCP server lets an agent call the Measurement API as tools instead, so conversions are exact and sourced. It uses the same API key, limits, and plans as the REST API. Create a free key to start.

Connect

Endpoint: https://mcp.unifyunits.com/mcp (Streamable HTTP). Authenticate with Authorization: Bearer uu_live_....

Claude Code:

bash

claude mcp add --transport http unifyunits https://mcp.unifyunits.com/mcp \
  --header "Authorization: Bearer $UNIFYUNITS_API_KEY"

Other clients that accept a remote server with a header (Cursor, VS Code) use the same URL and header. Claude Desktop can connect through mcp-remote:

json

{
  "mcpServers": {
    "unifyunits": {
      "command": "npx",
      "args": [
        "mcp-remote",
        "https://mcp.unifyunits.com/mcp",
        "--header",
        "Authorization:${AUTH}"
      ],
      "env": { "AUTH": "Bearer uu_live_..." }
    }
  }
}

Connectors that only support OAuth sign-in (such as the built-in connector list on claude.ai) are not supported yet.

Tools

Tool	Does	Plan
`convert_units`	Exact conversion between units	All
`parse_measurement`	Read "5 ft 11 in" and optionally convert	All
`normalize_quantity`	Multipacks, mixed units, ranges, locale decimals	All
`convert_currency`	ECB reference rates; historical dates need Developer	All
`list_units`, `list_substances`	Find unit and substance ids	All
`convert_substance`	Mass to volume with a sourced density	Developer+
`compare_unit_prices`	Rank offers by price per unit	Developer+

Every tool is read-only. Each takes the same fields as the matching REST endpoint, for example POST /v1/convert.

Limits and errors

Calls use your key, so they count against the same burst limit and monthly quota as REST calls. A successful call uses the same quota as the REST endpoint; failed calls are free.
API errors come back as tool results with isError set and the error code, for example PLAN_REQUIRED or QUOTA_EXCEEDED, so the agent can explain what happened.
Pass numbers as decimal strings. Currency rates are reference rates, and substance densities are reference values that vary with conditions; the tool results include the details.