Intervals.icu API Skill

Skill Relationship

┌─────────────────┐     fetch data      ┌───────────────────┐
│  intervals-icu  │ ──────────────────► │ cycling-training  │
│   (DATA API)    │                     │    (ANALYSIS)     │
│                 │ ◄────────────────── │                   │
│ • wellness      │   interpret results │ • zone calc       │
│ • activities    │                     │ • periodization   │
│ • power curves  │                     │ • workout design  │
│ • fitness       │                     │ • load management │
└─────────────────┘                     └───────────────────┘

Usage pattern:

1. Use intervals-icu to fetch data from API
2. Use cycling-training to analyze and interpret
3. Use intervals-icu to update wellness/events

API wrapper for intervals.icu cycling training platform. Designed to work alongside the cycling-training skill.

Quick Start

# Set credentials (one-time)
export INTERVALS_API_KEY="your_api_key"
export INTERVALS_ATHLETE_ID="iXXXXX"

# Use the API helper
~/.claude/skills/intervals-icu/scripts/api.sh wellness today
~/.claude/skills/intervals-icu/scripts/api.sh activities 2024-01-01 2024-01-31

Authentication

Get your API key from https://intervals.icu/settings → Developer Settings → API Key.

Find athlete ID in the URL when logged in: intervals.icu/athlete/iXXXXX/...

Rate Limiting

Intervals.icu API has rate limits. The script handles this with:

• Automatic retry with exponential backoff (default: 3 attempts)
• Configurable via INTERVALS_MAX_RETRIES environment variable

# Increase retries for bulk operations
export INTERVALS_MAX_RETRIES=5

If you hit rate limits frequently:

• Add delays between bulk requests: sleep 1
• Use date ranges instead of individual requests
• Cache responses locally for analysis

Prerequisites

• curl - Pre-installed on most systems
• jq - brew install jq (macOS) / apt install jq (Linux)
• bats-core - Optional, for tests: brew install bats-core

API Helper Script

Use scripts/api.sh to handle authentication and common operations:

Command	Description
api.sh wellness [date]	Get wellness for date (default: today)
api.sh wellness-range <start> <end>	Get wellness for date range
api.sh wellness-update <date> <json>	Update wellness fields
api.sh activities <start> <end> [format] [--all]	List activities (--all for pagination)
api.sh activity <id>	Get single activity details
api.sh activity-streams <id> [types]	Get activity data streams
api.sh activity-upload <file>	Upload activity (.fit, .gpx, .tcx)
api.sh athlete	Get athlete profile
api.sh fitness	Get current CTL/ATL/TSB
api.sh zones	Get power/HR zone settings
api.sh events <start> <end>	Get planned events/workouts
api.sh event-create <date> <json>	Create planned workout/event
api.sh power-curves <start> <end> [format]	Power curves (json/summary/seconds)

Examples

# Get today's wellness
~/.claude/skills/intervals-icu/scripts/api.sh wellness

# Get wellness for specific date
~/.claude/skills/intervals-icu/scripts/api.sh wellness 2024-01-15

# Update wellness (weight and sleep)
~/.claude/skills/intervals-icu/scripts/api.sh wellness-update 2024-01-15 '{"weight": 72.5, "sleepSecs": 28800}'

# Get last month's activities
~/.claude/skills/intervals-icu/scripts/api.sh activities 2024-01-01 2024-01-31

# Export activities as CSV
~/.claude/skills/intervals-icu/scripts/api.sh activities 2024-01-01 2024-01-31 csv > activities.csv

Direct curl Examples

For custom operations not covered by the helper:

# Base URL
BASE="https://intervals.icu/api/v1"

# Auth header
AUTH="Authorization: Basic $(echo -n "API_KEY:$INTERVALS_API_KEY" | base64)"

# Get power curve
curl -s -H "$AUTH" "$BASE/athlete/$INTERVALS_ATHLETE_ID/power-curves?oldest=2024-01-01&newest=2024-12-31"

# Get streams for activity
curl -s -H "$AUTH" "$BASE/activity/iXXXX/streams?types=watts,heartrate,cadence"

# Upload activity
curl -s -H "$AUTH" -F "file=@ride.fit" "$BASE/athlete/$INTERVALS_ATHLETE_ID/activities"

Key Endpoints Reference

Endpoint	Method	Purpose
/athlete/{id}	GET	Athlete profile
/athlete/{id}/wellness/{date}	GET/PUT	Wellness data
/athlete/{id}/wellness	GET	Wellness range (add ?oldest=&newest=)
/athlete/{id}/activities	GET	Activities list
/activity/{id}	GET	Activity details
/activity/{id}/streams	GET	Activity data streams
/athlete/{id}/events	GET	Planned workouts/events
/athlete/{id}/power-curves	GET	Power duration curves

Wellness Fields

Field	Type	Range	Description
weight	float	30-200 kg	Body weight
restingHR	int	30-100 bpm	Resting heart rate
hrv	float	10-150 ms	HRV RMSSD (typical: 20-80)
hrvSDNN	float	10-200 ms	HRV SDNN
sleepSecs	int	0-43200	Sleep duration (0-12h in seconds)
sleepScore	float	0-100	Sleep quality percentage
sleepQuality	int	1-5	1=poor, 5=excellent
fatigue	int	1-5	1=fresh, 5=exhausted
mood	int	1-5	1=bad, 5=great
motivation	int	1-5	Training motivation
readiness	int	1-5	Training readiness
stress	int	1-5	Stress level
soreness	int	1-5	Muscle soreness
ctl	float	0-200	Chronic Training Load (fitness)
atl	float	0-300	Acute Training Load (fatigue)
rampRate	float	-10 to +10	CTL weekly change rate

Integrate with cycling-training

Use both skills together:

1. Fetch data with intervals-icu skill:

   ~/.claude/skills/intervals-icu/scripts/api.sh wellness-range 2024-01-01 2024-01-31 > wellness.json
   ~/.claude/skills/intervals-icu/scripts/api.sh activities 2024-01-01 2024-01-31 > activities.json
   

2. Analyze with cycling-training skill:

   • Calculate training load distribution
   • Check polarization index
   • Evaluate recovery status based on HRV trends
   • Plan next mesocycle based on CTL/ATL/TSB

3. Update wellness after morning check-in:

   ~/.claude/skills/intervals-icu/scripts/api.sh wellness-update today '{"weight": 72.5, "sleepSecs": 28800, "readiness": 4}'
   

End-to-End Workflow Example

Complete example: Morning HRV-based workout adjustment using both skills.

Scenario

You wake up, check HRV, and want to adjust today's planned workout based on recovery status.

Step 1: Fetch morning wellness data

# Get today's wellness (HRV from device sync)
WELLNESS=$(~/.claude/skills/intervals-icu/scripts/api.sh wellness today)
echo "$WELLNESS" | jq '{hrv, restingHR, sleepSecs, ctl, atl}'

Output:

{
  "hrv": 42.5,
  "restingHR": 54,
  "sleepSecs": 25200,
  "ctl": 65.3,
  "atl": 72.1
}

Step 2: Analyze with cycling-training skill

Based on the data:

• HRV: 42.5 ms (below your baseline of 50 ms = -15%)
• TSB: 65.3 - 72.1 = -6.8 (slightly fatigued)
• Sleep: 7 hours (adequate but not optimal)

cycling-training recommendation: Reduce intensity. Convert threshold workout to endurance/recovery.

Step 3: Update today's planned event

# Find today's planned workout
TODAY=$(date +%Y-%m-%d)
EVENTS=$(~/.claude/skills/intervals-icu/scripts/api.sh events $TODAY $TODAY)
EVENT_ID=$(echo "$EVENTS" | jq -r '.[0].id')

# Update to easier workout
~/.claude/skills/intervals-icu/scripts/api.sh event-update "$EVENT_ID" '{
  "name": "Recovery Ride (HRV adjusted)",
  "description": "Original: Threshold intervals. Adjusted due to low HRV (-15% from baseline).",
  "icu_training_load": 40
}'

Step 4: Log subjective wellness

~/.claude/skills/intervals-icu/scripts/api.sh wellness-update today '{
  "readiness": 3,
  "fatigue": 3,
  "mood": 4,
  "soreness": 2
}'

Decision Matrix

HRV vs Baseline	TSB	Recommendation
>+10%	>0	Execute as planned or add intensity
±10%	>0	Execute as planned
±10%	<0	Execute but monitor
<-10%	Any	Reduce intensity or rest
<-20%	Any	Rest day

Testing

Run the test suite:

# Requires: bats-core
# Install: brew install bats-core (macOS) or apt install bats (Linux)

~/.claude/skills/intervals-icu/tests/run_tests.sh

Tests verify:

• Help and argument validation
• Environment variable checks
• Date parsing (cross-platform)
• JSON parsing with mock fixtures
• Power curve calculations

Troubleshooting

Common Errors

Error	Cause	Solution
HTTP 401	Invalid API key	Regenerate key in settings
HTTP 403	No permission	Check athlete ID ownership
HTTP 404	Resource not found	Verify date format (YYYY-MM-DD)
HTTP 429	Rate limited	Wait 60s, reduce request frequency
"jq: command not found"	jq not installed	brew install jq (macOS) / apt install jq (Linux)
Empty response	No data for date range	Check date range contains activities
"Invalid JSON"	Malformed JSON payload	Validate JSON: `echo '{"key": "value"}'

Debug Mode

Enable verbose output for debugging:

# Show curl commands
export INTERVALS_DEBUG=1
~/.claude/skills/intervals-icu/scripts/api.sh wellness today

Common Issues

Issue: Activities not syncing from Garmin/Wahoo

• Check device sync in intervals.icu settings
• Verify connection status with fitness platform
• Manual upload: api.sh activity-upload ride.fit

Issue: HRV not appearing in wellness

• HRV requires compatible device (Garmin, Wahoo, Oura, etc.)
• Check device sync completed before fetching
• Some devices sync HRV with delay (up to 2 hours)

Issue: Power curves show 0 for some durations

• Need activity with sustained effort at that duration
• Indoor trainers may have gaps in data
• Check activity streams: api.sh activity-streams <id> watts

Issue: CSV export has wrong encoding

• Intervals.icu returns UTF-8
• If Excel shows garbled text: Import as UTF-8, not auto-detect

Undocumented Endpoints

For endpoints not covered by api.sh, use Context7:

// Find Intervals.icu docs
mcp__plugin_context7_context7__resolve-library-id({
  libraryName: "intervals.icu"
})

// Query specific endpoint
mcp__plugin_context7_context7__query-docs({
  libraryId: "/websites/intervals_icu_api_v1",
  query: "how to create workout library entry"
})

Common Workflows

Morning Wellness Check-in

# Get HRV device data (if synced)
~/.claude/skills/intervals-icu/scripts/api.sh wellness today

# Update subjective metrics
~/.claude/skills/intervals-icu/scripts/api.sh wellness-update today '{"readiness": 4, "mood": 4, "soreness": 2}'

Weekly Training Review

# Get last 7 days
END=$(date +%Y-%m-%d)
START=$(date -v-7d +%Y-%m-%d 2>/dev/null || date -d "7 days ago" +%Y-%m-%d)

~/.claude/skills/intervals-icu/scripts/api.sh activities $START $END
~/.claude/skills/intervals-icu/scripts/api.sh wellness-range $START $END
~/.claude/skills/intervals-icu/scripts/api.sh fitness  # Current CTL/ATL/TSB

Export for Analysis

# CSV export for spreadsheet analysis
~/.claude/skills/intervals-icu/scripts/api.sh activities 2024-01-01 2024-12-31 csv > yearly_activities.csv
~/.claude/skills/intervals-icu/scripts/api.sh wellness-range 2024-01-01 2024-12-31 csv > yearly_wellness.csv