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Base URL

https://api.syncline.run
All API requests use HTTPS. HTTP requests will be redirected.

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Authentication

All endpoints (except /health) require an API key in the X-API-Key header. 
X-API-Key: sk_live_abc123...
See Authentication for details.

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Endpoints

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Core Endpoints

Find Availability

Find time slots where attendees are available

Schedule Meeting

Create a calendar event with Google Meet

Check Availability

Check a single user’s calendar

Update Preferences

Update user scheduling preferences

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Request Format

All POST requests use JSON: 
curl -X POST https://api.syncline.run/v1/availability \
  -H "X-API-Key: sk_live_abc123..." \
  -H "Content-Type: application/json" \
  -d '{"attendees": ["alice@example.com", "bob@example.com"]}'

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Response Format

All responses are JSON: 
{
  "slots": [...],
  "total_found": 5
}

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Error Handling

Errors follow this format: 
{
  "error": {
    "code": "invalid_attendees",
    "message": "Attendee list must contain exactly 2 email addresses",
    "field": "attendees"
  }
}

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HTTP Status Codes

CodeMeaning
200Success
400Bad Request - Invalid parameters
401Unauthorized - Invalid or missing API key
404Not Found - Resource doesn’t exist
429Rate Limit Exceeded
500Internal Server Error

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Rate Limits

  • Free Tier: 2M requests/month
  • Rate: 100 requests/minute per API key
Rate limit headers in response: 
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 95
X-RateLimit-Reset: 1700000000

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Pagination

Currently, all endpoints return complete results (no pagination needed). Typical response sizes:
  • find_mutual_availability: 5 slots
  • check_availability: Full day view
  • schedule_meeting: Single meeting object

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Idempotency

Meeting creation supports idempotency keys: 
curl -X POST https://api.syncline.run/v1/schedule \
  -H "Idempotency-Key: unique-request-id-123" \
  -H "X-API-Key: sk_live_abc123..." \
  ...
If you retry with the same key within 24 hours, you’ll get the original response (no duplicate meeting created).

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Timezones

All datetime fields use ISO 8601 format with timezone: 
{
  "start_time": "2025-11-20T10:00:00-08:00"
}
Syncline handles timezone conversion automatically. Users see times in their preferred timezone.

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Webhooks

Coming soon! Register webhooks to receive real-time updates about meetings.

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Client Libraries

Official SDKs coming soon:
  • Python
  • JavaScript/TypeScript
  • Go
  • Ruby
For now, use any HTTP client. See examples for reference implementations.

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Changelog

Track API changes:
  • v1.0.0 (2025-11-15): Initial release
Breaking changes will be announced 30 days in advance.

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Next Steps

Find Availability

Find mutual availability between users

Schedule Meeting

Create calendar events