Multisport Coach API

AI coach that creates personalized training plans for runners, cyclists, swimmers, and triathletes. This skill provides access to workout plans, performance metrics, AI coaching, and plan adaptation. Powered by Transition.

Authentication

Authenticated endpoints require the TRANSITION_API_KEY environment variable. Pass it as the X-API-Key header on every request. If it's not set, tell the user to generate one in the Transition app under Settings > API Keys.

Base URL: https://api.transition.fun

Free Endpoint (No Auth Required)

Workout of the Day

Generate a random structured workout. Each request returns a different workout.

curl "https://api.transition.fun/api/v1/wod?sport=run&duration=45"

Parameters:

• sport — run, bike, swim, or strength (default: run)
• duration — minutes, 10-300 (default: 45)

{
  "date": "2026-02-09",
  "sport": "run",
  "name": "Tempo Builder",
  "description": "Build aerobic endurance with sustained tempo efforts",
  "duration_minutes": 45,
  "intensity": "moderate",
  "segments": [
    {"name": "Warm-up", "duration_minutes": 9, "intensity": "easy", "description": "Easy jog to warm up"},
    {"name": "Tempo", "duration_minutes": 27, "intensity": "moderate", "description": "Steady tempo at comfortably hard pace"},
    {"name": "Cool-down", "duration_minutes": 9, "intensity": "easy", "description": "Easy jog to cool down"}
  ]
}

Authenticated Endpoints

Get Workouts

Retrieve scheduled workouts for a date range.

curl -H "X-API-Key: $TRANSITION_API_KEY" \
  "https://api.transition.fun/api/v1/workouts?start=2026-02-09&end=2026-02-15"

Parameters:

• start — Start date (YYYY-MM-DD, required)
• end — End date (YYYY-MM-DD, required)
• Maximum range between start and end is 90 days.

Get Workout Details

curl -H "X-API-Key: $TRANSITION_API_KEY" \
  "https://api.transition.fun/api/v1/workouts/123"

Generate Workouts

Trigger AI workout generation for the user's training plan.

curl -X POST -H "X-API-Key: $TRANSITION_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.transition.fun/api/v1/workouts/generate"

Adapt Workouts

Adapt the training plan based on recent performance or schedule changes.

curl -X POST -H "X-API-Key: $TRANSITION_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"reason": "feeling fatigued after race weekend"}' \
  "https://api.transition.fun/api/v1/workouts/adapt"

Check Generation Status

Poll whether workout generation/adaptation is complete.

curl -H "X-API-Key: $TRANSITION_API_KEY" \
  "https://api.transition.fun/api/v1/workouts/status"

Performance Management Chart (PMC)

Get CTL (fitness), ATL (fatigue), and TSB (form) data.

curl -H "X-API-Key: $TRANSITION_API_KEY" \
  "https://api.transition.fun/api/v1/performance/pmc"

Performance Stats

Get FTP, threshold paces, heart rate zones, and other metrics.

curl -H "X-API-Key: $TRANSITION_API_KEY" \
  "https://api.transition.fun/api/v1/performance/stats"

AI Coach Chat

Chat with the AI endurance coach. Returns a streaming response (SSE).

curl -X POST -H "X-API-Key: $TRANSITION_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"message": "Should I do intervals today or rest?"}' \
  "https://api.transition.fun/api/v1/coach/chat"

Chat History

curl -H "X-API-Key: $TRANSITION_API_KEY" \
  "https://api.transition.fun/api/v1/coach/history"

Athlete Profile

curl -H "X-API-Key: $TRANSITION_API_KEY" \
  "https://api.transition.fun/api/v1/profile"

Push Workout to Garmin

curl -X POST -H "X-API-Key: $TRANSITION_API_KEY" \
  "https://api.transition.fun/api/v1/workouts/123/push-garmin"

Rate Limits

Rate limit errors return HTTP 429 with a message indicating which limit was exceeded.

Tips for Agents

• Check fatigue before recommending hard workouts. Call GET /api/v1/performance/pmc and look at TSB (Training Stress Balance). If TSB is below -20, the athlete is likely fatigued — suggest easier workouts or rest.
• Use adapt sparingly. Plan adaptation regenerates the entire training plan using AI. Only trigger it when the athlete explicitly asks for changes or when there's a significant reason (injury, schedule change, race date change).
• Use the free WOD endpoint for casual users. If someone just wants a quick workout without signing up, use GET /api/v1/wod. No API key needed.
• Workout generation is async. After calling POST /workouts/generate or POST /workouts/adapt, poll GET /workouts/status until it returns ready, then fetch the workouts.
• Date format is always YYYY-MM-DD for all date parameters.