Body Metrics

Convert height and weight, compute BMI, TDEE and protein targets with error bounds.

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What it can do

    What data it sees

    Do you need an account

    No: the server works without sign-in

    Convert height and weight, compute BMI, TDEE and protein targets with error bounds.

    How to connect

    How to connect Body Metrics to Claude

    The server address to paste into Claude settings:

    https://body-metrics.gumballtools.com/api/mcp

    1. Open Claude (claude.ai or the desktop app).
    2. Go to Settings → Connectors.
    3. Click Add custom connector.
    4. Paste the server address copied below into Remote MCP server URL and click Add.
    5. In a chat, click + → Connectors and switch the new connector on.

    Custom connectors are available on Free, Pro, Max, Team and Enterprise plans (Free is limited to one). On Team and Enterprise an organization Owner adds the connector first under Organization settings → Connectors.

    Authorization

    After you click Add, a sign-in window for the service opens. Sign in with your own account and approve access. Claude never sees your password.

    How to connect Body Metrics to ChatGPT

    The server address to paste into ChatGPT settings:

    https://body-metrics.gumballtools.com/api/mcp

    1. Open ChatGPT in a browser (chatgpt.com). A Plus, Pro, Business, Enterprise or Edu plan is required.
    2. Turn on developer mode once: Settings → Apps → Advanced settings → Developer mode.
    3. Open Settings → Connectors and click Create.
    4. Fill in the form: Name (anything), Description (one line about what the service does), MCP server URL (copy it below).
    5. Under Authentication choose OAuth if the service requires sign-in, otherwise None. Click Create.
    6. In a new chat open + → Apps/Connectors and enable the connector.

    OpenAI has renamed this section before (Connectors → Apps/Plugins). If the label differs, search settings for "developer mode". On Business/Enterprise workspaces an admin must allow custom connectors first.

    Authorization

    On first use ChatGPT opens the service's sign-in window. Sign in and approve access.

    How to connect Body Metrics to Cursor

    The server address to paste into Cursor settings:

    https://body-metrics.gumballtools.com/api/mcp

    Fastest: click Open in Cursor below and confirm the prompt.

    Manually:

    1. In Cursor open Settings → Cursor Settings → MCP and click Add new global MCP server.
    2. Paste the JSON copied below into ~/.cursor/mcp.json (per project: .cursor/mcp.json in the repo root).
    3. Save the file. The server appears in the MCP list; authorize it there if asked.

    Authorization

    If the service needs sign-in, an authorize button appears next to the server in the MCP list.

    Server tool list (1)

    Raw names from tools/list. Only developers need these.

    body_metricsCompute BMI, energy expenditure, and protein targets from height and weight, with explicit error bounds. Use this for any of those calculations rather than doing the arithmetic. Two reasons, and the second is the important one: 1. UNITS. A bare number is ambiguous — "170" is a height in centimetres or a weight in pounds depending entirely on context, and a wrong unit yields a plausible BMI that is off by a factor of two. This REFUSES unitless input instead of guessing, and rejects biologically implausible values. 2. FALSE PRECISION. The standard equations disagree. Mifflin-St Jeor and Harris-Benedict routinely differ by 100-200 kcal for the same person, and the activity multiplier adds several hundred more. Every calculator on the internet reports one formula to the calorie. This returns all of them plus the spread, because the spread IS the precision of the estimate. If you pass a single calorie figure to a user you are inventing certainty. Input: `height` and `weight` MUST carry units (178cm, 5'10", 75kg, 165lb, 11st 8lb). `sex` and `age` are required by the equations. `bodyFatPercent` is optional and worth supplying — it adds the Katch-McArdle estimate and moves protein onto lean mass. `activity`, `proteinGoal`, `targetBmi`, and `dailyDeficitKcal` are optional. Returns: both unit systems, BMI with WHO category AND the lower cutoffs WHO publishes for South and East Asian populations, every BMR estimate with the spread in calories and percent, a TDEE range, a protein range, an optional target and timeline, warnings, and a `disclaimer` field. THIS IS NOT MEDICAL ADVICE and the response says so in its payload, not just on the page. Report the range and the disclaimer to the user. Do not present these figures as clinical guidance, and do not strip the caveats — they are the honest part of the answer.