cronometer-api-mcp

cronometer-api-mcp

Hosted version for Claude.ai, ChatGPT, and Grok coming soon. Join the waitlist →

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="[e-mail]"
export CRONOMETER_PASSWORD="your-password"

Optional: override the account timezone

Diary entries are stamped in your Cronometer account's timezone, which the server reports at login. If that zone is wrong (for example, an older build had reset it) you can force a specific IANA zone without changing your account settings:

export CRONOMETER_ACCOUNT_TZ="America/Los_Angeles"

When set, this takes precedence over both the value reported at login and any cached session, so it also overrides a stale cached timezone.

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": "[e-mail]",
        "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 by supergateway (see Dockerfile), which owns the HTTP listener and exposes MCP streamable-HTTP at /mcp. The server has no built-in authentication — any remote deployment must sit behind 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