BMIkit
Model Context Protocol

BMI Kit MCP server

Connect BMI Kit to Claude, ChatGPT and other AI assistants. Compute body composition (BMI, body fat, FFMI, waist to height) and, when signed in, save and track measurements over time.

Server URL
https://bmikit.com/api/mcp
In your AI assistant
Give me the honest body composition picture: 180 cm, 85 kg, 35, male, waist 95 cm.
BMI
26.2
Overweight
23%
Body fat
0.53
Waist/ht
20.1
FFMI
via BMI Kit MCP
Endpoint
https://bmikit.com/api/mcp
Transport
Streamable HTTP
Auth
OAuth 2.1 (public tools need none)
Discovery
/.well-known/mcp
Reference

Tools

compute_body_metricsRead only

Compute a fuller body composition picture from height, weight, age and sex: BMI and its WHO category, estimated body fat percentage, fat free mass index (FFMI), and with a waist measurement the waist to height ratio, plus optional BMR, TDEE, ideal weight and daily macro targets. Returns a general wellness estimate only, not medical advice and not patient specific.

Parameters
heightrequired
number
cm for metric, inches for imperial (see units).
weightrequired
number
kg for metric, pounds for imperial.
agerequired
integer
Years (2 to 120).
sexrequired
"male" | "female"
Used by the body composition formulas.
unitsoptional
"metric" | "imperial"
Defaults to metric.
waistoptional
number
Circumference. Enables waist to height and Navy body fat.
neckoptional
number
With waist, enables U.S. Navy body fat.
hipoptional
number
Women only, improves Navy body fat.
activityoptional
"sedentary".."veryActive"
Enables TDEE and macro targets.
goaloptional
"lose" | "maintain" | "gain"
With activity, enables macro targets.
honest_pictureRead only

Explain in plain language what BMI alone misses for this person, covering body fat percentage, waist to height ratio and FFMI, with cited sources (WHO, Deurenberg 1991, Ashwell and NICE). Returns a general wellness estimate only, not medical advice and not patient specific.

Parameters
heightrequired
number
cm for metric, inches for imperial (see units).
weightrequired
number
kg for metric, pounds for imperial.
agerequired
integer
Years (2 to 120).
sexrequired
"male" | "female"
Used by the body composition formulas.
unitsoptional
"metric" | "imperial"
Defaults to metric.
waistoptional
number
Circumference. Enables waist to height and Navy body fat.
neckoptional
number
With waist, enables U.S. Navy body fat.
hipoptional
number
Women only, improves Navy body fat.
activityoptional
"sedentary".."veryActive"
Enables TDEE and macro targets.
goaloptional
"lose" | "maintain" | "gain"
With activity, enables macro targets.
save_measurementWrites dataSign in

Save a body measurement (weight, optional waist, neck, hip and measured body fat) to the signed in user's BMI Kit history, so trends can be tracked over time. Optionally store height, sex and age once, which lets later trends include BMI, FFMI and lean mass. Requires the user to be signed in and to have consented to storing body composition data. General wellness tracking, not medical advice.

Parameters
weightrequired
number
kg or pounds per units.
unitsoptional
"metric" | "imperial"
Defaults to metric.
taken_onoptional
string (YYYY-MM-DD)
Defaults to today.
waistoptional
number
Waist circumference.
neckoptional
number
Neck circumference.
hipoptional
number
Hip circumference.
body_fat_pctoptional
number
Measured body fat, if known.
heightoptional
number
Stored once on your profile for derived trends.
sexoptional
"male" | "female"
Stored once on your profile.
ageoptional
integer
Stored once on your profile.
get_trendsRead onlySign in

Summarise the signed in user's saved measurements over time for one metric (weight, BMI, body fat, FFMI, lean mass or waist to height ratio), including direction of change and a muscle at risk note when a large share of weight lost appears to be lean mass. General wellness estimate only, not medical advice and not patient specific.

Parameters
metricoptional
"weight" | "bmi" | "body_fat" | "ffmi" | "lean_mass" | "whtr"
Defaults to weight.
range_daysoptional
integer
Lookback window. Omit for all history.
Why save with BMI Kit

Memory turns a calculator into a tracker

Calculations are useful once. The value compounds when the assistant remembers. Saving to your BMI Kit account gives any assistant a real body composition history to reason about.

One history, every assistant

Log a weigh in from ChatGPT, ask Claude about the trend next week, see the same numbers on the web. Your measurements are not stuck in one chat.

Beyond the scale

Trends track FFMI, lean mass, body fat and waist to height, not just weight. The assistant can reason about body composition, not a single number.

Catch muscle loss early

On GLP-1 or any cut, get_trends flags when too much of the weight lost looks like lean mass, so you can add protein and resistance work in time.

Your data, your control

Stored in the EU, isolated per user, opt in only. Export or delete it whenever you want. Calculations without saving keep nothing at all.

Setup

Connect in a minute

Claude

Settings, Connectors, Add custom connector, then paste the server URL. In Claude Code:

claude mcp add --transport http \
  bmikit https://bmikit.com/api/mcp

ChatGPT

Settings, Connectors, enable Developer mode, Add a connector, paste the server URL, then complete the sign in.

Cursor and VS Code

Add to your MCP config:

{
  "bmikit": {
    "url": "https://bmikit.com/api/mcp"
  }
}
Examples

Try asking

Trust

Privacy and your data

Calculations store nothing

The calculation tools process the numbers in your request and keep nothing. No account needed.

Saving is opt in

Storing measurements needs sign in and explicit consent. Data is held in the EU, isolated per user, and you can withdraw or delete it any time.

Wellness, not diagnosis

A general wellness tool, not medical advice and not patient specific. Please consult a qualified healthcare professional.