> ## 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. # Get a combined platform + exchange fee quote for a prospective trade > Prices a trade you are considering WITHOUT submitting it: for a market order (`order_type=market`, `price` omitted) the live orderbook is walked for `quantity` to compute a size-weighted executable price; for a limit order (`order_type=limit`) `price` is required and used as the resting quote. Shares the exact computation used by the WebSocket RFQ stream (`subscribe_fee_quote`), so the two surfaces can never price a trade differently. Quotes are display-only, degrade-open estimates (`is_estimate: true`) — the authoritative fee is computed at fill time. If no fresh orderbook is available, every numeric field is a `"0"` placeholder and `pricing_unavailable: true`; callers MUST check that flag rather than rendering the zeros as a real quote. Supported `exchange_id` values: `polymarket`, `kalshi`, `predictfun`. **Auth & scope.** Requires `trade:read`. ## OpenAPI ````yaml /openapi/execution.yaml get /orders/fee-quote openapi: 3.1.0 info: title: Kairos Order Execution API version: 1.0.0 summary: >- Order entry, cancellation, fee quotes, and live position exposure across venues. description: > The Order Execution API at `execution.kairos.trade` places and manages orders across every venue Kairos integrates. Two lanes: - **Custodial** (`POST /orders`) — Kairos signs and routes on your behalf (custodial signing). Async ack: a 200 means validated + enqueued; track via `GET /orders/{order_id}` or the WebSocket order/fill stream. - **Self-custody / external signing** (`POST /v2/orders/intent` + `POST /v2/orders/submit`) — for allow-listed institutional accounts on Polymarket and Predict.fun: Kairos builds the EIP-712 payload, you sign with your own key, submission is synchronous with the venue's verbatim result. `POST /v2/onchain/intent` + `POST /v2/onchain/submit` are the same pattern for on-chain operations (approvals, redeem, split/merge, unwrap) on Polygon, where you also pay the gas. ## Authentication All endpoints require a Kairos API key (`X-Client-Id` + `X-Api-Key` + `X-Api-Secret`) or a first-party session JWT, plus the per-operation scope (`trade:execute`, `trade:read`, `position:read`) where the operation documents one. Synthetic Books accepts any otherwise-valid account credential without an extra scope or allowlist. There is no anonymous tier. Scope checks apply to API-key credentials only; a session JWT carries no scope list and is treated as holding every scope. The custodial mutation endpoints (`POST /orders`, the three cancel endpoints) and Synthetic Books create/refresh/release carry an additional `RequireServiceToken` gate satisfied by **any** of: the full API-key triple, an internal `X-Service-Token`, or a valid `X-Csrf-Token`. API-key consumers need no extra header — but a bare `Authorization: Bearer ` alone is NOT sufficient on those routes. The `/v2/orders/*` and `/v2/onchain/*` external-signing routes have no such gate: a session JWT alone works there. ## Rate limits Order submission is capped per user (default 5 orders per **second**, sliding window, `ORDER_RATE_LIMIT_PER_SEC`); some credentials carry an `orders` override, which is enforced on its own per-credential window of the same duration *in addition to* the per-user window — either one denying is a `429`. Idempotent replays (same `client_order_id`) return the existing order before the limiter runs and never consume a slot. The limiter is Redis-backed and **fails closed**: if Redis is unreachable the submission is denied with `429`. Separately, repeated *authentication failures* from one client IP are throttled at 10 failures per 60 s (also fail-closed). That limiter returns the minimal `{"error": "Too many authentication attempts"}` body. **No rate-limit headers.** This service does not emit `Retry-After`, `X-RateLimit-*`, or any other backoff hint on a `429` — back off on your own schedule. ## Error responses **Six different error body shapes are in use across this service and they are not interchangeable.** Check the shape documented on the specific operation before writing a parser; a client that assumes one shape will read `undefined` for the reason on the others. 1. `OrderErrorResponse` — the structured envelope (`error`, `code`, `error_details{code,message,details?,metadata?,actions}`) returned by every handler that surfaces an `ExecutionError`/`ApiError`: order submission, cancel-all, the CTF endpoints, the Polymarket/Opinion onboarding endpoints, Hyperliquid withdraw/transfer, and most of the deposit-wallet family. Note the two `code` fields differ in case: top-level `code` is PascalCase (`"AuthInsufficientScope"`), while `error_details.code` is the SCREAMING_SNAKE_CASE wire code (`"AUTH_INSUFFICIENT_SCOPE"`). Match on `error_details.code`. 2. `OrderSimpleErrorResponse` — the minimal `{"error": "..."}` (sometimes with `code`) used by the auth middleware (any endpoint's `401`/`403`/`429`), the whole `/v2/*` external-signing and on-chain lane, the Kalshi and Predict.fun endpoints. 3. `OrderMarketLinkErrorResponse` — `{"message": "..."}`, with no `error` and no `code`. Used by `POST /orders/market-links` **only**. 4. **Empty or plain-text, not JSON at all.** Several deposit-wallet endpoints — most importantly the RPC signed-batch submission and `POST /exchanges/polymarket/imported/relay-info` — return most 4xx/5xx responses with a **completely empty body** and `content-type: text/plain`. A handful of cases carry a bare plain-text sentence (`batch is not an allowed withdrawal or collateral conversion`, `relayer rejected batch: …`). Do not attempt to JSON-parse these. 5. Handlers whose Rust signature returns a bare `StatusCode` likewise send **no body at all**; those responses are marked "empty body (status code only)". 6. `SyntheticBookErrorResponse` — `{"error": "stable_snake_case_code", "message": "...", "details"?: {...}}` on `/v1/synthetics*`. Match the top-level `error`; upstream definition validation may be nested under `details`. A further wrinkle inside shape 1: some provider-access checks discard the specific reason and return a generic `"Request failed with status 403"` / `AUTH_CREDENTIALS_INVALID` body, while others preserve `AUTH_INSUFFICIENT_SCOPE` and the real message. Do not rely on the message text of an access denial being stable. The central `ExecutionError` → HTTP mapping (`ApiError::from`) is: | `ExecutionError` | Status | `error_details.code` | |---|---|---| | `InsufficientBalance` | 400 | `FUNDS_INSUFFICIENT_USDC` | | `CollateralLocation` | 400 | `FUNDS_COLLATERAL_LOCATION` | | `InvalidOrder` | 400 | `VALIDATION_INVALID_ORDER` | | `PositionShortfall` | 400 | `FUNDS_INSUFFICIENT_BALANCE` | | `MarketClosed` | 400 | `EXCHANGE_POLYMARKET_MARKET_CLOSED` | | `OrderAlreadyCancelled` | 400 | `VALIDATION_INVALID_ORDER` | | `UnsupportedExchange` | 400 | `EXCHANGE_UNSUPPORTED` | | `SlippageExceeded` | 400 | `MARKET_FOK_NOT_FILLED` | | `FokNotFilled` | 400 | `MARKET_FOK_NOT_FILLED` | | `AuthenticationError` | 401 | `AUTH_CREDENTIALS_INVALID` | | `CredentialError` | 401 | `AUTH_CREDENTIALS_NOT_FOUND` | | `MarketNotFound` | 404 | `VALIDATION_MARKET_NOT_FOUND` | | `OrderNotFound` | 404 | `VALIDATION_INVALID_ORDER` | | `MarketNotSettledOnChain` | 409 | `VALIDATION_MARKET_NOT_SETTLED_ON_CHAIN` | | `OrderbookUnavailable` | 422 | `ORDERBOOK_UNAVAILABLE` | | `ExchangeError` (code `429`/`RATE_LIMITED`) | 429 | `EXCHANGE_POLYMARKET_RATE_LIMITED` | | `ExchangeError` (code `401`/`UNAUTHORIZED`) | 401 | `AUTH_POLYMARKET_API_KEY_INVALID` | | `SigningError` | 500 | `SIGNATURE_ERROR` | | `DatabaseError` | 500 | `DATABASE_ERROR` | | `InternalError` / `LedgerReconciliationRequired` / `SponsoredRequestWedged` / `PreTradeError` | 500 | `INTERNAL_ERROR` | | `NetworkError`, `ExchangeError` (any other code) | 502 | `NETWORK_ERROR` / venue-classified | | `LockError` | 503 | `INTERNAL_ERROR` | | `Timeout` | 504 | `NETWORK_TIMEOUT` | A venue `ExchangeError` is further classified from the venue's own message text before it is mapped, so an "allowance is not enough" rejection becomes `ALLOWANCE_CTF_NOT_SET`, a "not enough balance" rejection becomes `FUNDS_INSUFFICIENT_BALANCE`, "post-only mode" becomes `MARKET_NOT_READY`, a "no liquidity" rejection becomes `MARKET_INSUFFICIENT_LIQUIDITY`, and so on. Match on `error_details.code`, never on `error`. ## Server-level guards Every request is subject to a 120 s timeout (`OE_REQUEST_TIMEOUT_SECS`), a 2 MiB request-body cap (`OE_MAX_BODY_BYTES`, over-size bodies get `413`), and a 1024-request global concurrency ceiling (`OE_MAX_CONCURRENT_REQUESTS`). Every response carries `X-Content-Type-Options: nosniff`, `X-Frame-Options: DENY`, HSTS, and a `default-src 'none'` CSP. ## Conventions - Prices are decimal strings on the 0–1 scale; `*_bps` fields are the same value in basis points (× 10000). - Quantities/sizes are decimal strings. - Structured errors carry `error_details.code` (SCREAMING_SNAKE_CASE) plus actionable recovery `actions`. ## Changelog **2026-09-14 — collateral routing fields on `POST /orders`.** Four optional request fields and one optional response field. `collateral` (`skip` | `check` | `fund`) **defaults to** `skip`, which is exactly today's path: no affordability check, no hold, no funding, zero added latency — so no existing caller changes behaviour without opting in. `shard_funding` **defaults to** `true`, which is also exactly today's behaviour: the Kalshi shard move is same-venue, zero-fee and already runs for every account; send `false` to opt out. `collateral=fund` requires both `max_bridge_fee_usdc` and `max_funding_wait_ms` and is rejected `400` naming the missing cap; either cap without `fund` is likewise a `400`. The response gains `funding`, `null` whenever no funding work ran. FIX sessions carry the same fields on `NewOrderSingle(D)` as optional tags `5701`–`5704`; a session that sends none of them is unchanged. contact: name: Kairos url: https://app.kairos.trade/docs/api-reference termsOfService: https://kairos.trade/terms servers: - url: https://execution.kairos.trade description: Production (central primary, us-east-1) - url: https://eu-west-1-polymarket.executor.kairos.trade description: >- Production regional execution node — Ireland, colocated with Polymarket. Same API surface; assigned at onboarding. - url: https://ap-northeast-1-predictfun.executor.kairos.trade description: >- Production regional execution node — Tokyo, colocated with Predict.fun. Same API surface; assigned at onboarding. - url: https://staging-execution.kairos.trade description: Staging security: - apiKeyClientId: [] apiKeyKey: [] apiKeySecret: [] paths: /orders/fee-quote: get: tags: - Orders summary: Get a combined platform + exchange fee quote for a prospective trade description: >- Prices a trade you are considering WITHOUT submitting it: for a market order (`order_type=market`, `price` omitted) the live orderbook is walked for `quantity` to compute a size-weighted executable price; for a limit order (`order_type=limit`) `price` is required and used as the resting quote. Shares the exact computation used by the WebSocket RFQ stream (`subscribe_fee_quote`), so the two surfaces can never price a trade differently. Quotes are display-only, degrade-open estimates (`is_estimate: true`) — the authoritative fee is computed at fill time. If no fresh orderbook is available, every numeric field is a `"0"` placeholder and `pricing_unavailable: true`; callers MUST check that flag rather than rendering the zeros as a real quote. Supported `exchange_id` values: `polymarket`, `kalshi`, `predictfun`. **Auth & scope.** Requires `trade:read`. operationId: getFeeQuote parameters: - name: exchange_id in: query required: true description: One of `polymarket`, `kalshi`, `predictfun`. schema: type: string enum: - polymarket - kalshi - predictfun example: polymarket - name: market_id in: query required: false description: >- Condition id (Polymarket). Required for Polymarket if `token_id` is omitted. schema: type: string - name: token_id in: query required: false description: >- CLOB token id (Polymarket) — preferred over `market_id` for book/fee lookup. schema: type: string example: '71360012345678901234567890123456789012345678901234567890123456' - name: quantity in: query required: true description: Decimal string. Number of shares/contracts to quote. Must be > 0. schema: type: string example: '100' - name: side in: query required: true description: >- The quote is side-aware (walks the ask side for buy, the bid side for sell). schema: type: string enum: - buy - sell example: buy - name: price in: query required: false description: >- Decimal string in `(0, 1]`. Required when `order_type=limit` (the resting price). Omit for `order_type=market` to have the server price off the live book. schema: type: string example: '0.52' - name: order_type in: query required: true description: >- `market` (taker, priced from the book) or `limit` (maker, priced at `price`). schema: type: string enum: - market - limit example: market responses: '200': description: Combined platform + exchange fee quote. content: application/json: schema: $ref: '#/components/schemas/OrderFeeQuoteResponse' '400': description: >- Unsupported `exchange_id`, invalid `order_type`/`side`, non-positive `quantity`, `price` out of `(0, 1]`, a limit order missing `price`, or a Polymarket quote missing both `token_id` and `market_id`. Empty body (status code only) — the specific validation failure is logged server-side but never returned. '401': $ref: '#/components/responses/ExecUnauthorized' '403': description: >- Missing `trade:read` scope, or API-key access to this provider is disabled. Empty body (status code only). '503': description: >- API-key access to this provider could not be checked (fails closed). Empty body (status code only). components: schemas: OrderFeeQuoteResponse: type: object description: >- Response for `GET /orders/fee-quote`. All numeric fields are decimal strings in USDC. The WebSocket `subscribe_fee_quote` stream emits a near-identical frame, but it omits `venue_reserve_fee_usdc` — do not treat the two as interchangeable. See `execution-ws.asyncapi.yaml`. required: - avg_price_usdc - filled_size - requested_size - sufficient_liquidity - notional_usdc - platform_fee_usdc - exchange_fee_usdc - venue_reserve_fee_usdc - total_fee_usdc - total_cost_usdc - pricing_unavailable - is_estimate - funding_tier - bridge_fee_usdc - bridge_eta_p50_ms - bridge_eta_p95_ms - bridge_route_label - bridge_min_txs - bridge_eta_state - bridge_quote_unavailable - bridge_beta properties: avg_price_usdc: type: string description: >- Size-weighted executable price (VWAP for a market order), or the limit price for a limit order. example: '0.52' filled_size: type: string description: >- Size the book can actually fill; equals `requested_size` when liquidity suffices. example: '100' requested_size: type: string description: The size the caller asked to quote (echoes `quantity`). example: '100' sufficient_liquidity: type: boolean description: False when the book cannot fill the full `requested_size`. notional_usdc: type: string description: '`filled_size × avg_price_usdc`.' platform_fee_usdc: type: string description: >- Kairos platform fee, based on the caller's fee tier. `"0"` if the tier lookup failed (fails open, never a phantom rate). exchange_fee_usdc: type: string description: >- Venue-specific fee the caller is expected to pay. `"0"` on venues that only charge takers when this quote is a resting maker order. venue_reserve_fee_usdc: type: string description: >- Fee the VENUE actually reserves to accept the order — distinct from `exchange_fee_usdc`. Some venues (Polymarket CLOB) can't know a resting limit will stay maker, so they reserve the taker estimate at placement regardless; buy-affordability checks must size off this field, not `exchange_fee_usdc`. total_fee_usdc: type: string description: '`platform_fee_usdc + exchange_fee_usdc`.' exchange_fee_note: type: string nullable: true description: Human-readable note on the exchange fee, e.g. "1.8% taker fee". total_cost_usdc: type: string description: >- All-in cost — for a buy, `notional + fees`; for a sell, `proceeds = notional − fees`. pricing_unavailable: type: boolean description: >- `true` when no executable price was available (no client price and no fresh orderbook) — every other numeric field is a placeholder `"0"` and MUST NOT be rendered as a real quote. is_estimate: type: boolean description: >- Always `true` — this is a display estimate; the authoritative fee is computed at fill time. funding_tier: type: string enum: - t0_local - t1_prepositioned - t2_bridge - reject description: >- Which rails run to fund this order. `t0_local` means no collateral moves; only `t2_bridge` carries a bridge fee. It names the movement, not whether the balance suffices. bridge_fee_usdc: type: string nullable: true description: >- Bridge fee in USDC. `"0"` below `t2_bridge`, and `null` exactly when `bridge_quote_unavailable` is `true` — an unknown fee is never rendered as `$0.00`. This fee is already included in `total_cost_usdc`, and buy-affordability checks must include it too. bridge_eta_p50_ms: type: integer nullable: true description: >- Median bridge fill time from Kairos's own completed intents, never a provider estimate. Present only once the route has ≥1,000 samples and its p90 ETA error is within ±10s. bridge_eta_p95_ms: type: integer nullable: true description: >- 95th-percentile bridge fill time from Kairos's own completed intents. Present under the same gate as `bridge_eta_p50_ms`. bridge_route_label: type: string nullable: true description: >- The route in the user's words, naming the token the rail DELIVERS, e.g. "BNB USDT → Polymarket pUSD via Relay". Absent when nothing bridges. bridge_min_txs: type: integer nullable: true description: >- On-chain transactions the bridge route needs, so a client can price the signing path. Absent when nothing bridges. bridge_eta_state: type: string nullable: true enum: - measured - not_yet_measured description: >- Whether the ETA above is a measurement or an admission that the route has not earned one. Absent when nothing bridges. bridge_quote_unavailable: type: boolean description: >- `true` when a bridge is needed and no quote landed. Consumers MUST render a "routing…" state and disable submit rather than showing any fee; `bridge_fee_usdc` is `null` in this state. bridge_beta: type: boolean description: >- `true` while tier-2 bridge funding is behind a flag, so the bridge row can be labelled beta. responses: ExecUnauthorized: description: > No valid credential presented — missing/invalid API-key headers or an invalid/expired session token. content: application/json: schema: type: object required: - error properties: error: type: string example: Unauthorized 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. apiKeySecret: type: apiKey in: header name: X-Api-Secret description: 64-char hex API secret. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.