Body fat

Tool id: body-fat · Methods: navy, jackson-pollock-3, deurenberg

Estimate body-fat percentage from body measurements; reach for it to track composition or to unlock LBM-based TDEE methods.

Input

Field	Type	Notes
sex	"male" | "female"	required
age	number | null	years, 0–120 — needed for jackson-pollock-3 and deurenberg
height	{ value, unit } | null	cm or in — needed for navy and deurenberg
weight	{ value, unit } | null	kg or lb — needed for deurenberg
neck	{ value, unit } | null	circumference — needed for navy
waist	{ value, unit } | null	circumference — needed for navy
hip	{ value, unit } | null	circumference — required for navy when sex is "female"
skinfold_sum	number | null	mm, sum of 3 sites — needed for jackson-pollock-3
methods	string[] | "all"	defaults to "all"

Methods

• navy — US Navy circumference method (Hodgdon & Beckett). Uses neck/waist (plus hip for women).
• jackson-pollock-3 — Jackson & Pollock (1978), 3-site skinfold.
• deurenberg — Deurenberg (1991), a BMI-based estimate.

Each method needs different inputs (circumferences vs skinfolds vs weight+height+age). Any method whose required inputs are absent appears in skipped.

Example

TypeScript

import { REGISTRY } from "@almostjacked/fitness-tools";
const bodyFat = REGISTRY.get("body-fat")!;
bodyFat.compute(bodyFat.input.parse({
  sex: "male",
  neck:   { value: 40, unit: "cm" },
  waist:  { value: 90, unit: "cm" },
  height: { value: 180, unit: "cm" },
}));

curl

curl -s localhost:8080/v1/tools/body-fat \
  -X POST -H 'content-type: application/json' \
  -d '{"sex":"male","neck":{"value":40,"unit":"cm"},"waist":{"value":90,"unit":"cm"},"height":{"value":180,"unit":"cm"}}'

MCP

Call the body-fat tool with these arguments:

{
  "sex": "male",
  "neck": { "value": 40, "unit": "cm" },
  "waist": { "value": 90, "unit": "cm" },
  "height": { "value": 180, "unit": "cm" }
}

{
  results: [
    { method: "navy", value: 18.37, unit: "%", detail: null },
  ],
  consensus: { mean: 18.37, median: 18.37, min: 18.37, max: 18.37, n: 1 },
  skipped: [
    { method: "jackson-pollock-3", reason: "jackson-pollock-3: requires skinfold_sum and age" },
    { method: "deurenberg",        reason: "deurenberg: requires weight, height, age" },
  ],
}

Call it another way

Full docs for the other protocols: HTTP API · MCP server.