> ## Documentation Index > Fetch the complete documentation index at: https://docs.kairos.trade/llms.txt > Use this file to discover all available pages before exploring further. # Liveness probe > Trivially cheap liveness check used by the load balancer. Touches no dependencies and is never rate-limited. ## OpenAPI ````yaml /openapi/market-data-api.yaml get /health openapi: 3.1.0 info: title: Kairos Market Data API version: 1.2.0 summary: Read-only prediction and perpetual market data across venues. description: > The Kairos Market Data API provides read-only access to normalized prediction-market data across every venue Kairos integrates: OHLCV candles, the trade tape, market metadata, resolution lifecycles, and latest mark prices. ## No signup required Every endpoint works **without credentials** on the anonymous free tier, rate-limited per source IP (120 light units/min, 20 heavy units/min). Try any request from the interactive docs at [app.kairos.trade/docs/market-data](https://app.kairos.trade/docs/market-data) or straight from curl. For production budgets (1,200 light and 150 heavy units/min by default, raisable per credential), request an API key from the Kairos team. ## Authentication Three modes, resolved per request: - **Anonymous** — no credential headers at all. Free tier, IP-keyed limits. - **API key** — `X-Client-Id` + `X-Api-Key` + `X-Api-Secret` headers (all three; partial header sets are rejected with 401 rather than degrading to anonymous). - **First-party session** — `Authorization: Bearer` JWT (Kairos web app sessions only; not offered to API consumers). Resolution order is fixed: an `Authorization` header takes the bearer path, any of the three API-key headers takes the API-key path, and only a request carrying neither is eligible for the anonymous tier. On the API-key path, an unreachable credential store surfaces on **any** endpoint as `500` with `code: internal` and the message `authentication backend unavailable`. A source IP outside a credential's whitelist is `403 ip_not_whitelisted`; that is the only 403 this service emits. ## Rate limiting Weighted sliding-window budgets over one minute, in **units**, across two independent buckets: light (candles, metadata, resolutions, trade metrics) and heavy (trade history, marks, perpetual snapshots). Most requests cost 1 unit; larger requests may consume more of your quota — each operation's `x-kairos-rate-limit` states its exact cost model. Every admitted response carries `X-RateLimit-Bucket`, `X-RateLimit-Tier`, `X-RateLimit-Remaining`, and `X-RateLimit-Reset`; 429s add `Retry-After`. A separate per-IP admission gate runs *before* authentication to keep a flood off shared infrastructure. It also answers 429 `rate_limited`, but with `Retry-After: 60` and no `X-RateLimit-*` headers. Redis backs the weighted limiter and it fails **closed**: if it is unreachable the request is rejected with 503 `rate_limiter_unavailable` rather than let through unmetered. ## Conventions - **Prediction-market prices** are on the 0–100 scale (implied probability × 100) in the prediction candle, trade, and mark endpoints. Prediction USD notional = `size × price / 100`. - **Perpetual prices are direct venue prices**, not probabilities and not 0–100 values. Perpetual quantities retain their declared native unit (`base_asset` or `contracts`). Never divide a perpetual price by 100 or compute contract notional without the instrument's authoritative contract multiplier; the snapshot does not synthesize a cross-venue notional. - **Hyperliquid is two products on one venue.** Its HIP-4 outcome markets are prediction markets, read with `provider=hyperliquid` on the prediction endpoints; its perpetuals are bare coins read under `/v1/perpetuals/hyperliquid/{instrument}/snapshot`, where the instrument is the canonical id `hl-mainnet--` (e.g. `hl-mainnet-btc-usdt`). Different id schemes, different price semantics; they are never interchangeable. - **Errors** all use one envelope: `{"error": {"code": "...", "message": "..."}}`. - **Providers** are case-insensitive; `kalshi_offchain` aliases `kalshi`, `dome` aliases `polymarket`, and `opinion` is resolvable for historic reads only. contact: name: Kairos url: https://app.kairos.trade/docs/market-data termsOfService: https://kairos.trade/terms servers: - url: https://md.kairos.trade description: Production - url: https://staging-md.kairos.trade description: Staging security: - {} - apiKeyClientId: [] apiKeyKey: [] apiKeySecret: [] tags: - name: Candles description: OHLCV candle series (1s → 1d), JSON or compact columnar binary. - name: Trades description: Trade tape and aggregate volume metrics. - name: Markets description: Market metadata, batch lookup, identifier resolution, and enumeration. - name: Resolutions description: Resolution outcomes and UMA-style lifecycle state/timelines. - name: Marks description: Latest mark (last trade price) per outcome token. - name: Perpetuals description: Live perpetual books, trades, candles, funding, and market state. Beta. - name: Status description: Health and readiness probes. paths: /health: get: tags: - Status summary: Liveness probe description: > Trivially cheap liveness check used by the load balancer. Touches no dependencies and is never rate-limited. operationId: getHealth responses: '200': description: Service is up. content: application/json: schema: type: object required: - status properties: status: type: string example: ok security: [] components: securitySchemes: apiKeyClientId: type: apiKey in: header name: X-Client-Id description: >- Credential client id (`kairos_ck_...`). Must be sent together with X-Api-Key and X-Api-Secret. apiKeyKey: type: apiKey in: header name: X-Api-Key description: >- 64-char hex API key. Must be sent together with X-Client-Id and X-Api-Secret. apiKeySecret: type: apiKey in: header name: X-Api-Secret description: >- 64-char hex API secret. Must be sent together with X-Client-Id and X-Api-Key. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.