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Prefer WebSocket for order submission. Placing and cancelling orders over the persistent /ws socket is lower-latency (one round trip instead of the REST submit/poll pair) and simpler to build: one connection, one auth handshake, and pushed order_update/fill events instead of polling. See Order Execution over WebSocket.
Kairos exposes several API services. Each has its own base URL, authentication model, pagination style, and error envelope — the only thing genuinely shared is the API-key header triple. This page maps them; the navigation holds the hand-written guides and the OpenAPI-generated endpoint references.
The four API groups below the overview are generated from the OpenAPI specs, so they always reflect the current wire contract — parameters, request bodies, and responses. The Guides beneath them add the caveats that don’t fit in a schema: pagination quirks, field casing, price scales, and error handling. Read the generated page for the exact fields, then the matching guide for the gotchas.

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Your first request

The Market Data API needs no credentials — call it right now:
For an authenticated service, send the API-key triple on every request:

Submit an order

The exact request shape, status semantics, and error codes for the custodial order lane.

Stream market data

Real-time orderbooks, trades, and prices over WebSocket with protobuf encoding.

Fees and fee quotes

Platform tiers, per-venue exchange fees, and the live fee-quote endpoint.

Get an API key

API keys, scopes, the session JWT, and how each service reports auth failures.

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Machine-readable specifications

Every public API is described by an OpenAPI 3.1 specification. The copies below power the auto-generated endpoint references; download them to generate clients or feed your own tooling.
WebSocket surfaces are described separately with AsyncAPI. See the WebSocket section for the wire contracts and Protobuf Schema for the generated message definitions.

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What trips people up first

These bite almost every first integration. Each links to the guide with the full detail.
  • price is required on every order — including market orders, where it is the limit you are willing to cross, not a sentinel. Omitting it is a 400. See Orders.
  • Tick grids change while a market trades. Read ranges and min_tick (and treat them as decimal strings, not floats), not a single cached tick size. See Markets, Resolutions & Marks.
  • Casing is per-service. /orders and most REST is snake_case; /combo/* is camelCase; the RPC API uses camelCase. Copy the generated reference for the service you’re calling. See Combos & Parlays.
  • Price scales differ by surface. Candles and trades are on a 0–100 scale; marks and resolution payouts are 0–1; some discovery feeds return camelCase with a 24h suffix. See Markets & Prices.
  • A bad credential triple on an execution mutation is 403, not 401. Handle both. See Orders.
  • The fastest way to trade is the WebSocket. Submit and cancel over /ws instead of the REST submit/poll pair. See Order Execution over WebSocket.

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Conventions

  • Authentication — the Market Data API is anonymous and free. The Data and Execution APIs accept the API-key triple; Agora requires a first-party session JWT; the RPC API accepts either. Scopes are per-operation. See API Key Auth.
  • Pagination — mixed. The Market Data API, /markets/active, /trades/kalshi, and /matched-markets are cursor-based (pass the returned next_cursor back as cursor). Most Data API list endpoints and all RPC list procedures use limit/offset.
  • Errors — each service has its own envelope: Execution returns error_details.code, the Data API returns {"detail": ...}, the Market Data API returns {"error": {"code", "message"}}, and the RPC API returns a tRPC error with error.data.code. Status codes are standard HTTP.
  • Rate limits — per-IP on the free tier, per-key on authenticated tiers. Honor 429 with exponential backoff.