cronometer-api-mcp

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An MCP (Model Context Protocol) server for Cronometer nutrition tracking, built on the reverse-engineered mobile REST API.

Unlike cronometer-mcp, which takes a comprehensive GWT-RPC approach against Cronometer's web backend, this server talks to the same JSON REST API used by the Cronometer Android app -- with clean payloads and stable, versioned endpoints.

Features

Food log -- diary entries with food names, amounts, meal groups
Nutrition data -- daily macro/micro totals and nutrition scores with per-nutrient confidence
Food search -- search the Cronometer food database, get detailed nutrition info
Diary management -- add/remove entries, copy days, mark days complete
Custom foods -- create foods with custom nutrition data
Macro targets -- read weekly schedule and saved templates
Fasting -- view history and aggregate statistics
Biometrics -- weight, body fat, heart rate, and other tracked metrics over a date range

Quick Start

1. Install uv

curl -LsSf https://astral.sh/uv/install.sh | sh

2. Set credentials

export CRONOMETER_USERNAME="[email protected]"
export CRONOMETER_PASSWORD="your-password"

3. Configure your MCP client

uvx downloads and runs the server on demand -- no separate install step.

OpenCode (`opencode.json`)

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "cronometer": {
      "type": "local",
      "command": ["uvx", "cronometer-api-mcp"],
      "environment": {
        "CRONOMETER_USERNAME": "{env:CRONOMETER_USERNAME}",
        "CRONOMETER_PASSWORD": "{env:CRONOMETER_PASSWORD}"
      },
      "enabled": true
    }
  }
}

Claude Desktop (`claude_desktop_config.json`)

{
  "mcpServers": {
    "cronometer": {
      "command": "uvx",
      "args": ["cronometer-api-mcp"],
      "env": {
        "CRONOMETER_USERNAME": "[email protected]",
        "CRONOMETER_PASSWORD": "your-password"
      }
    }
  }
}

Available Tools

Food Log & Nutrition

Tool	Description
`get_food_log`	Diary entries for a date, each enriched with food name, source, serving measure/count, and that food's per-entry nutrient contribution, plus an energy_summary (target/consumed/remaining kcal) and a nutrition_summary of consumed totals for every tracked nutrient
`get_daily_nutrition`	Consumed macro and micronutrient totals for every nutrient tracked in Cronometer
`get_nutrition_scores`	Category scores (Vitamins, Minerals, etc.) with per-nutrient consumed amounts and confidence levels

Food Search & Details

Tool	Description
`search_foods`	Search the Cronometer food database by name
`get_food_details`	Full nutrition profile and serving sizes for a food

Diary Management

Tool	Description
`add_food_entry`	Log a food serving to the diary
`remove_food_entry`	Remove one or more diary entries
`add_custom_food`	Create a custom food with specified nutrition
`copy_day`	Copy all entries from the previous day
`mark_day_complete`	Mark a diary day as complete or incomplete

Targets & Tracking

Tool	Description
`get_macro_targets`	Weekly macro schedule and saved target templates
`get_fasting_history`	Fasting history within a date range
`get_fasting_stats`	Aggregate fasting statistics
`list_biometrics`	List trackable biometric metrics and their units
`get_biometrics`	Biometric time series (e.g. weight, body fat) within a date range

All date parameters use YYYY-MM-DD format and default to today when omitted.

Transport

stdio only. For remote/hosted use, the stdio server is wrapped bysupergateway (see Dockerfile),which owns the HTTP listener and exposes MCP streamable-HTTP at /mcp. Theserver has no built-in authentication — any remote deployment must sitbehind an authenticating gateway or reverse proxy.

Development

For local development, copy .env.example to .env and fill in your credentials:

cp .env.example .env
# edit .env
uv run cronometer-api-mcp

The CLI auto-loads .env on startup (dev convenience only). Real environment variables always win over .env, so production deployments and MCP client env blocks are unaffected.

How It Works

This server communicates with mobile.cronometer.com -- the same REST API used by the Cronometer Android/Flutter app. The API was reverse-engineered through:

Static analysis of libapp.so (Dart AOT snapshot) from the APK to discover endpoint names
Traffic interception via Frida + mitmproxy to capture exact request/response formats
Trial-and-error against the live API to confirm payload shapes

The API uses two protocols:

v2 (POST /api/v2/*) -- JSON-body auth, used for most operations (food search, diary read/write, nutrition, fasting, macros, biometrics)
v3 (DELETE /api/v3/user/{id}/*) -- Header-based auth (x-crono-session), used for diary entry deletion

Python API

You can use the client directly:

from cronometer_api_mcp.client import CronometerClient
from datetime import date

client = CronometerClient()

# Search for foods
results = client.search_food("chicken breast")

# Get food details
food = client.get_food(results[0]["id"])

# Log a serving
client.add_serving(
    food_id=food["id"],
    measure_id=food["defaultMeasureId"],
    grams=200,
)

# Get today's diary
diary = client.get_diary()

# Get nutrition scores
scores = client.get_nutrition_scores()

License

MIT

cronometer-api-mcp