API Overview

Complete REST API reference

Base URL

https://api.syncline.run

All API requests use HTTPS. HTTP requests will be redirected.

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.

Endpoints

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

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": ["[e-mail]", "[e-mail]"]}'

Response Format

All responses are JSON:

{
  "slots": [...],
  "total_found": 5
}

Error Handling

Errors follow this format:

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

HTTP Status Codes

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

Rate Limits

• Rate: 100 requests/minute per API key (varies by plan)

Rate limit headers in response:

X-RateLimit-Limit: 100
X-RateLimit-Remaining: 95
X-RateLimit-Reset: 1700000000

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

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).

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.

Webhooks

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

Client Libraries

Official SDKs coming soon:

• Python
• JavaScript/TypeScript
• Go
• Ruby

For now, use any HTTP client. See examples for reference implementations.

Changelog

Track API changes:

• v1.0.0 (2025-11-15): Initial release

Breaking changes will be announced 30 days in advance.

Next Steps

Find Availability

Find mutual availability between users

Schedule Meeting

Create calendar events