fitness-app-tools - SKILL.md Agent Skill

name: fitness-app-tools description: Provides reference GitHub repositories, food nutrition APIs, and fitness calculation formulas for building Qt/QML fitness apps. Use when developing diet logging, exercise tracking, macro calculation, BMR/MET, or integrating Open Food Facts/USDA FoodData Central.

Fitness App Development Tools

Reference repositories, APIs, and formulas for fitness app development with Qt/QML and C++. Apply when implementing nutrition tracking, exercise logging, or calorie/macro calculations.

1. Reference GitHub Repositories

Repo	Description	Tech
LiftLog	Gym activity tracking, exercise logging	C++, Qt 5.x, QML, Qt Quick Controls 1
QML-OpenFitnessPal	FOSS MyFitnessPal alternative, diet + macro tracking	QML, Android
fitness_planner	Qt-based gym planner	Qt, GPL-2.0
QtHealth	Cross-platform health/fitness data access (HealthKit, etc.)	Qt, plugin system
openfoodfacts-server	Open Food Facts backend/API reference	Server-side

When to reference: Architecture patterns, QML layout for diet/exercise screens, storage models, API client structure.

2. Food & Nutrition APIs

Open Food Facts

Docs: https://openfoodfacts.github.io/openfoodfacts-server/api/
Search: GET https://world.openfoodfacts.org/cgi/search.pl?search_terms={query}&search_simple=1&json=1
Product by barcode: GET https://world.openfoodfacts.org/api/v2/product/{barcode}.json
Rate limits: ~10 req/min search, ~100 req/min product; no auth for read.
Data: product.nutriments (energy_100g, proteins_100g, carbohydrates_100g, fat_100g), Nutri-Score.

USDA FoodData Central

Docs: https://fdc.nal.usda.gov/api-guide
Search: GET https://api.nal.usda.gov/fdc/v1/foods/search?api_key={key}&query={query}
Food details: GET https://api.nal.usda.gov/fdc/v1/food/{fdcId}?api_key={key}
Requirements: Free API key from data.gov; 1,000 req/hour per IP.
Data: foodNutrients array with nutrient IDs (e.g. 1003=protein, 1005=carb, 1004=fat).

3. Fitness Calculation Formulas

Macro & Calorie

calories_per_portion = (energy_100g / 100) × portion_grams
protein_g = (proteins_100g / 100) × portion_grams
carb_g = (carbohydrates_100g / 100) × portion_grams
fat_g = (fat_100g / 100) × portion_grams

BMR (Mifflin-St Jeor)

male:   10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5
female: 10 × weight(kg) + 6.25 × height(cm) - 5 × age - 161

Exercise calories (MET-based)

calories_burned = 0.0175 × MET × weight(kg) × duration_minutes

Common MET values: walking 2.0–3.5, jogging 7.0, running 5mph 8.3, cycling 5.8, swimming 5.8.

Full MET table: Compendium of Physical Activities or see reference.md.

4. Quick Workflow

Choose data source: Open Food Facts for packaged products; USDA FDC for generic foods.
Implement API client in src/services/ (e.g. FoodSearchService); use QNetworkAccessManager.
Store locally in SQLite via StorageService; cache search results and fetched products.
Expose to QML via Q_PROPERTY or context property; keep UI in qml/pages/, qml/components/.
Follow project conventions: See qt-code-standards skill for Qt/QML/C++ structure.

5. Additional Reference

API response structures, full MET table, and integration examples: reference.md