> ## Documentation Index > Fetch the complete documentation index at: https://docs.agg.market/llms.txt > Use this file to discover all available pages before exploring further. # Get live midpoints for multiple markets > Returns live orderbook midpoints for the requested venue market IDs. `venueMarketIds` accepts either a comma-separated string (`?venueMarketIds=a,b,c`) or repeated params (`?venueMarketIds=a&venueMarketIds=b`). Midpoint represents the Yes-side price (0-1). Direct GET callers should keep batches small enough to stay under CDN URL limits; AGG SDK/UI clients default to 75 IDs per request and merge multiple batches automatically. Pass `bestPrice=true` to also receive top-of-book `bestBid`/`bestAsk` on every entry, per-outcome row, and matched sibling, plus `arbReturn` — the live, quality-gated cross-venue arbitrage return for the market's cluster, computed fresh by the engine on this request. Prefer it over the `arbReturn` embedded in venue-event listings, which is synced by a background job and can be stale. Every entry carries `marketStatus`; resolved markets never serve a price — they return null prices plus a structured `error` (`code: "market_resolved"`), and unknown ids return `code: "market_not_found"`, mirroring GET /orderbooks. Returns 503 if the orderbook engine is unavailable. ## OpenAPI ````yaml /openapi/openapi.json get /midpoints openapi: 3.0.2 info: title: AGG API version: 1.0.0 description: >- Prediction market aggregator REST API — authentication, users, venue events, venue markets, orderbooks, charts, and execution workflows. servers: - url: https://api.agg.market description: Production - url: https://api.staging.agg.market description: Staging security: [] paths: /midpoints: get: tags: - Orderbook summary: Get live midpoints for multiple markets description: >- Returns live orderbook midpoints for the requested venue market IDs. `venueMarketIds` accepts either a comma-separated string (`?venueMarketIds=a,b,c`) or repeated params (`?venueMarketIds=a&venueMarketIds=b`). Midpoint represents the Yes-side price (0-1). Direct GET callers should keep batches small enough to stay under CDN URL limits; AGG SDK/UI clients default to 75 IDs per request and merge multiple batches automatically. Pass `bestPrice=true` to also receive top-of-book `bestBid`/`bestAsk` on every entry, per-outcome row, and matched sibling, plus `arbReturn` — the live, quality-gated cross-venue arbitrage return for the market's cluster, computed fresh by the engine on this request. Prefer it over the `arbReturn` embedded in venue-event listings, which is synced by a background job and can be stale. Every entry carries `marketStatus`; resolved markets never serve a price — they return null prices plus a structured `error` (`code: "market_resolved"`), and unknown ids return `code: "market_not_found"`, mirroring GET /orderbooks. Returns 503 if the orderbook engine is unavailable. operationId: getMidpoints parameters: - name: venueMarketIds in: query required: true schema: anyOf: - type: string - type: array items: type: string - name: bestPrice in: query required: false schema: type: boolean responses: '200': description: '200' content: application/json: schema: type: object required: - data properties: data: type: array items: type: object required: - venueMarketId - venue - midpoint - spread - timestamp - outcomes - matched properties: venueMarketId: type: string venue: type: string midpoint: type: number nullable: true spread: type: number nullable: true timestamp: type: number nullable: true outcomes: type: array items: type: object required: - venueMarketOutcomeId - label - midpoint properties: venueMarketOutcomeId: type: string label: type: string midpoint: type: number nullable: true markSource: type: string enum: - local - local_merged - local_one_sided - sibling - local_boundary - none bookQuality: type: string enum: - healthy - bid_only - ask_only - endpoint_stub - wide_spread - crossed - empty bestBid: type: number nullable: true bestAsk: type: number nullable: true matched: type: array items: type: object required: - venueMarketId - venue - midpoint properties: venueMarketId: type: string venue: type: string midpoint: type: number nullable: true outcomes: type: array items: type: object required: - venueMarketOutcomeId - midpoint properties: venueMarketOutcomeId: type: string label: type: string midpoint: type: number nullable: true bestBid: type: number nullable: true bestAsk: type: number nullable: true bestBid: type: number nullable: true bestAsk: type: number nullable: true markSource: type: string enum: - local - local_merged - local_one_sided - sibling - local_boundary - none siblingVenueMarketId: type: string bestBid: type: number nullable: true bestAsk: type: number nullable: true arbReturn: type: number nullable: true marketStatus: type: string enum: - open - closed - resolved - unopened - paused error: type: object required: - code - message - retryable properties: code: type: string enum: - market_resolved - market_not_found message: type: string retryable: type: boolean '400': description: '400' content: application/json: schema: type: object required: - message properties: message: type: string '401': description: '401' content: application/json: schema: type: object required: - message properties: message: type: string '503': description: '503' content: application/json: schema: type: object required: - code - message - retryable properties: code: type: string enum: - orderbook_service_unavailable message: type: string retryable: type: boolean security: - appId: [] components: securitySchemes: appId: type: apiKey in: header name: x-app-id description: Your application ID. Required for all app-tier and user-tier routes. ````