--- title: "OutBIG for developers and agents" description: "Everything on the OutBIG board is public, so everything on it is readable programmatically without an account, an API key or a rate-limit negotiation. This page is the whole developer surface in on..." canonical: "https://outbig.bid/en/docs" language: "en" --- # OutBIG for developers and agents Everything on the OutBIG board is public, so everything on it is readable programmatically without an account, an API key or a rate-limit negotiation. This page is the whole developer surface in one place: a read-only JSON API, an OpenAPI 3.1 description of it, Markdown content negotiation on every page, and a plain-language guide for AI agents at /llms.txt. ## OutBIG JSON API Base URL `https://outbig.bid/api/v1`. No authentication, no API key, CORS open to any origin. Every response — including every error — is `application/json`. `GET /api/v1` — index: every endpoint with its absolute URL. `GET /api/v1/leaderboard` — the all-time board. Query: limit, offset, category, country, q. `GET /api/v1/today` — the rolling board for the previous 24 hours, with no midnight reset. Query: limit, offset, category. `GET /api/v1/categories` — the fixed category catalogue with counts and top amounts. `GET /api/v1/categories/{slug}` — one category and its ranking. `GET /api/v1/listings/{identityKey}` — one listing, with global and category rank. `GET /api/v1/activity` — the newest paid bids. `GET /api/v1/stats` — active listings, board value and clicks, all-time and today. ## OpenAPI specification The full machine-readable description lives at `https://outbig.bid/openapi.json`, and also at `https://outbig.bid/api/openapi.json`. It is OpenAPI 3.1: every operation has a unique `operationId` and a description, every parameter is typed with its bounds and an example, and every response — success and error alike — has a schema. That is what a model needs to expose these endpoints as callable functions. ## Site tools (WebMCP) When this marketplace is open in a supported built-in browser, ChatGPT Work or Codex can discover four structured Site Tools: `search_outbig_listings`, `get_outbig_listing`, `compare_outbig_listings`, and `explain_outbig_placement_options`. Availability still depends on the desktop app, model, account, workspace and rollout; ordinary browsers keep the same interface without these tools. Every OutBIG Site Tool is read-only. Search, read and comparison call the existing `/api/v1` endpoints, so they inherit the same active-listing, moderation, locale and placement rules as the public website. The placement explainer uses the same public board statistics and shared price rules as the interface. There are deliberately no Site Tools for checkout, payment, free-listing submission, sponsor reservation, deletion or moderation. Listing titles and descriptions can originate outside OutBIG and are marked as untrusted tool content; a paid rank is still not a review score or endorsement. ## Pace, not a quota We ask for at most 600 requests per minute. Every response carries `RateLimit-Limit`, `RateLimit-Remaining`, `RateLimit-Reset` and `RateLimit-Policy`, so you can keep to it without waiting to be refused; an instance that does see too many answers `429` with `Retry-After`. It is deliberately not a hard ceiling, and we would rather say so than imply one. Each server instance counts on its own, and requests spread across instances — measured 25 Aug 2026, twenty concurrent calls each reported a fresh counter. You can therefore exceed the figure without ever seeing a `429`. Read the headers as what the instance answering you has seen, and the number as the rate we ask you to keep. If that ever stops being enough for us, we will make it a real ceiling and say so here first. ## Versioning and deprecation The surface is versioned in the path (`/api/v1`). Breaking changes get a new version — `/api/v1` will not change shape underneath you. If a version is ever retired, the `Deprecation` and `Sunset` headers (RFC 8594) will be sent for at least six months before it stops answering, and this page will say so. Additive changes — a new field, a new endpoint — can happen at any time: ignore fields you do not know rather than failing on them. The full policy — what counts as breaking, what can change without notice, and how you will hear about it — is at `https://outbig.bid/en/deprecation`. ## Error format Errors never return HTML — not even at an address that does not exist. The body is always `{ "error": { "code", "message", "hint", "status" } }`. Branch on `error.code` — it is stable. `error.message` says what went wrong, `error.hint` says what to do instead, because repeating an identical request rarely helps. ## Markdown content negotiation Every page on this site also exists as Markdown. Send `Accept: text/markdown` and the same URL answers `text/markdown; charset=utf-8` with `Vary: Accept, Accept-Encoding`; send a browser's Accept header and it answers HTML. Quality values are honoured, and a request that accepts neither representation gets `406` with the list of what is available. Clients that cannot set headers can fetch the same documents directly under `https://outbig.bid/md/en/…`. ## Command-line tool `npx outbig top` reads the board without an installation, an account or a key. Add `--json` to any command for the raw API response. Commands: `top`, `today`, `categories`, `show `, `activity`, `stats`, `open`. There is deliberately no command to place a bid — for the same reason the API has no endpoint for it. ## Agent interfaces (MCP, A2A, NLWeb) The board answers over the protocols agents already speak, not only over plain HTTP. `https://outbig.bid/mcp` is an MCP server on Streamable HTTP with six read tools over the live board; `https://outbig.bid/mcp?surface=docs` is a second one over these pages and the policies. Neither needs a key, and neither can place a bid. `https://outbig.bid/a2a` accepts A2A `message/send`, and `https://outbig.bid/ask` implements Microsoft's NLWeb protocol with SSE streaming — both answer a question in plain language and return the figures the answer was built from. If you would rather enumerate than guess: `https://outbig.bid/.well-known/ard.json` catalogues every agentic resource, `https://outbig.bid/.well-known/api-catalog` is an RFC 9727 linkset, and `https://outbig.bid/.well-known/mcp/server-card.json` previews the MCP server before you open a transport. There is deliberately no OAuth metadata on this domain and the API never answers `401`. Those documents describe a protected resource; this one is not protected, and publishing them would send you looking for an authorization server that does not exist. `https://outbig.bid/auth.md` says so in full. ## Guidance for AI agents `https://outbig.bid/llms.txt` states what OutBIG is a good source for and, just as explicitly, what it is not: rank here is bought, not earned, and must never be presented as a review score or an endorsement. `https://outbig.bid/api/llms.txt` and `https://outbig.bid/docs/llms.txt` are the same thing scoped to one area. Every page also has a Markdown address: append `.md` (`https://outbig.bid/en/rules.md`), or start at `https://outbig.bid/index.md`. Listing pages keep the `/md/` form, because `.md` is also a country domain and would be ambiguous there. Add `?mode=agent` to any address for a machine-readable summary instead of markup. Bidding is a card payment and is deliberately not exposed as an API — an agent should hand that step to a person. --- ## Machine-readable entry points - Agent guide (what OutBIG is for): https://outbig.bid/llms.txt - OpenAPI 3.1 specification: https://outbig.bid/openapi.json - JSON API index: https://outbig.bid/api/v1 - Sitemap (all pages, both languages): https://outbig.bid/sitemap.xml - Developer documentation: https://outbig.bid/en/docs Every page on this site serves this Markdown when the request carries `Accept: text/markdown`.