{"uid":"cap_gB9toXuBM-gMUEHovv8BR","slug":"2s-prediction-market-probability-watcher-08f0bf38","name":"2s Prediction Market Probability Watcher","description":"The (most) everything API: 575+ pay-per-call endpoints for AI agents — ground-truth data, a full AI gateway, and agent infrastructure (storage, queues, watchers). USDC via x402, no signup, no API keys, and upto billing: pay actual usage, not the quote.","url":"https://2s.io/api/watchers/prediction-market","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"label":{"type":"string","maxLength":64,"description":"Optional free-text tag."},"payload":{"type":"object","description":"Arbitrary JSON echoed back in every callback.","additionalProperties":{}},"maxFires":{"type":"integer","maximum":1000,"minimum":1,"description":"Stop after this many callbacks (default 1)."},"threshold":{"type":"number","maximum":1,"minimum":0,"description":"Probability 0–1 to cross, e.g. 0.8."},"callbackUrl":{"type":"string","maxLength":2048,"description":"Signed event POSTed here (verify X-2s-Signature). Any http(s) URL."},"conditionId":{"type":"string","maxLength":80,"minLength":3,"description":"Polymarket market conditionId (from predict.market / predict.markets)."},"outcomeIndex":{"type":"integer","maximum":50,"minimum":0,"description":"Which outcome to watch (0 = first, usually Yes). Default 0."},"conditionType":{"enum":["above","below"],"type":"string","description":"Fire when the probability goes above or below the threshold."},"expiresInSeconds":{"type":"integer","maximum":7776000,"minimum":60,"description":"Active window in seconds (default 30d, max 90d)."}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.125","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.125/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.125","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.125","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_NI4FMwMBqRDM2BmPRnOXa","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.125","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Registers a webhook-based watcher that fires a signed callback when a Polymarket prediction market outcome crosses a specified probability threshold.","exampleAgentPrompt":"Set up a watcher on the Polymarket market with conditionId '0x1234abc...' — fire a webhook to https://myserver.com/hooks/pm when the first outcome (Yes) goes above 0.75 probability, up to 3 times, and tag it 'election-alert'.","exampleUseCases":null,"resultDescription":"A watcher registration is created; when the monitored Polymarket outcome's probability crosses the specified threshold, 2s POSTs a signed event to the callbackUrl containing the event details and the echoed payload object. The X-2s-Signature header lets you verify authenticity. No synchronous data is returned beyond confirmation of registration.","failureModes":["Invalid or unknown conditionId — watcher fails to bind to a market","callbackUrl unreachable or rejecting POSTs — callbacks silently fail or retry","Threshold out of range (not 0–1) — validation error","expiresInSeconds exceeds 90-day maximum — rejected","maxFires exceeds 1000 — rejected","Market resolves before threshold is crossed — watcher expires without firing","Signature verification failure on receiving end — caller bug, not API bug"],"whenToPreferThis":"Use this endpoint when you need event-driven, asynchronous alerts on Polymarket prediction market probability movements without polling. It is ideal for agents or workflows that need to react to market sentiment shifts (e.g., trigger downstream actions when a market crosses a conviction threshold). Prefer this over manual polling when you need reliable, signed delivery with configurable fire counts and expiry.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-14T19:08:29.607Z","isFirstParty":false}