Overview
First Leeward API reference.
REST API with JSON request and response bodies.
Base URL
| Environment | Base URL |
|---|---|
| Production | https://api.firstleeward.com/v0/ |
All requests are made against this single base URL.
Required Headers
Every request must include:
| Header | Description |
|---|---|
Authorization | Your API key as a Bearer token: Bearer YOUR_API_KEY |
Leeward-Version | API version in YYYY-MM-DD format. Current version: 2026-09-18 |
Content-Type | application/json for requests with a body |
Example Request
curl https://api.firstleeward.com/v0/users \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Leeward-Version: 2026-09-18"
Numerical Values
Monetary and rate fields use different JSON types depending on what they represent, chosen so partners never silently lose precision:
| Field shape | JSON type | Notes |
|---|---|---|
| Fiat amounts (USD, EUR, ...) | number | At the currency's native precision (2 decimal places for most fiat). Safe to read as a JS number. |
| Crypto and virtual asset amounts | string | Decimal string padded to the asset's decimals (e.g. "1.000000" for 1 USDC). Lossless across all values; compare and arithmetic via a big-decimal library. |
| Exchange and conversion rates | number | 6 decimal places. |
A field's individual description always wins when it differs. The same conventions are followed on input bodies.