POSTERIOR · DEVELOPERS DESK

API OPEN

The API · v1

Supported MLB evidence, piped straight into your stack.

Structured access to Posterior’s supported probabilities, immutable decisions, market states, public evidence and player context. The public OpenAPI operation documents ten bearer-protected production operations. Active keys default to 100 requests per minute, with stable JSON contracts across the v1 lifecycle. Public proof remains available separately through the delayed ledger and accuracy record.

API sandbox

Inspect the contract before a key exists.

Inspect the public schema and delayed evidence before a key exists, then compare them with representative bearer-protected request shapes. Production endpoints require active Pro plus the Builder add-on.

GET · public schema

/api/v1/openapi.json

Public OpenAPI 3.1 contract for the complete v1 operation catalog.

No key is required for the OpenAPI schema or delayed public CSV. Production v1 operations use POSTERIOR_KEY; API keys are one-time reveal secrets, so store them in an environment variable.

Open public resource OpenAPI schema

Sandbox request

GET /api/v1/openapi.json
Accept: application/json

Sandbox response

{
  "openapi": "3.1.0",
  "info": { "title": "Posterior API", "version": "v1" },
  "paths": { "/api/v1/picks/today": { "get": { ... } } }
}

OpenAPI schema Public CSV receipt

Selected endpoints · v1

MethodPathCache

GET

/api/v1/picks/today

Tonight's STRONG/LEAN slate + v0 NRFI + pitcher-K predictions, with signal breakdown.

30s cache

GET

/api/v1/player/{id}

Player memory: current posterior, true-talent trajectory, recent prediction ledger, and survival diagnostics.

1m cache

GET

/api/v1/accuracy

Live Brier score, win-rate by tier, model EV at close. Same numbers the public dashboard renders.

2m cache

GET

/api/v1/calibration

Calibration buckets — predicted-vs-actual rates per probability bin. Plot it however you want.

5m cache

The public OpenAPI 3.1 contract at /api/v1/openapi.json is the complete operation catalog. The examples above are four representative bearer-protected endpoints, not the entire API.

Quickstart

Issue a key at /mlb/account, then pipe the secret into a Bearer header. The same request, three idioms:

curl

$ curl -H "Authorization: Bearer $POSTERIOR_KEY" \    https://posterior.pro/api/v1/picks/today

typescript

const res = await fetch(
  "https://posterior.pro/api/v1/picks/today",
  { headers: { Authorization: `Bearer ${process.env.POSTERIOR_KEY}` } }
);
const { picks, ext_markets } = await res.json();

for (const pick of picks) {
  console.log(
    pick.decision.action,
    pick.decision.fair_price.label,
    pick.decision.best_line.label
  );
}

python

import os, httpx
r = httpx.get(
    "https://posterior.pro/api/v1/picks/today",
    headers={"Authorization": f"Bearer {os.environ['POSTERIOR_KEY']}"},
)
slate = r.json()

Response shape (truncated):

json

{
  "api_version": "v1",
  "generated_at": "2026-05-26T17:42:11.103Z",
  "game_date_et": "2026-05-26",
  "picks": [
    {
      "prediction_id": "pred_01HXJ6V…",
      "batter_name": "Aaron Judge",
      "team_name": "New York Yankees",
      "market": "1plus_hits",
      "p_predicted": 0.7124,
      "sharp_consensus_prob": 0.6680,
      "sharp_book_american_odds": -110,
      "sharp_source_book": "FanDuel",
      "tier": "STRONG",
      "signals": {
        "park_adj": 1.04,
        "pitcher_adj": 0.96,
        "lineup_confirmed": true,
        "form_adj": 1.06,
        "weather_adj": 0.98
      },
      "decision": {
        "action": "BET",
        "is_actionable": true,
        "reason": "Qualified edge with a captured playable line.",
        "fair_price": { "american_odds": -248, "label": "-248 fair" },
        "best_line": {
          "bookmaker": "FanDuel",
          "american_odds": -110,
          "label": "FanDuel -110",
          "captured": true
        },
        "market_trust": {
          "label": "Core",
          "note": "Highest-trust season-ledger family."
        },
        "context": {
          "badges": ["Lineup confirmed", "Recent form +6%"],
          "lineup_confirmed": true,
          "form_adj": 1.06,
          "weather_adj": 0.98,
          "game_state": "PRE"
        },
        "proof": [
          "Model 71.2%",
          "Sharp 66.8%",
          "Edge +4.4pp",
          "STRONG tier"
        ]
      }
    }
  ],
  "ext_markets": { "moneylines": [ ... ], "nrfi": [ ... ], "strikeouts": [ ... ] }
}

AI-native

Wire Posterior into an agent, Discord bot, notebook, or internal dashboard with ordinary HTTPS fetches. Your tool asks what Posterior says about tonight's slate; the API returns model probabilities with the calibration receipt attached.

Note: Packaged SDKs and agent integrations are not advertised as live until their packages, manifests, and install paths are published. For launch, the supported contract is the REST v1 surface and OpenAPI schema.

What you get

Builder exposes supported, versioned machine contracts rather than promising that every website field exists in every endpoint. Responses preserve the same evidence and uncertainty boundaries used by the product; coverage is defined by the published OpenAPI schema.

Public OpenAPI, the delayed resolved CSV, and the public record can be inspected without a Builder key. Production operations require active Pro plus the Builder add-on; standard activation does not require a manual application. The current contract also includes bearer-protected, non-actionable win-probability JSON and SVG-card widget operations. The calibration receipt at /mlb/accuracy is the load-bearing public claim on both sides. Subscriber and API exports may not be resold, scraped, mirrored, or bulk-republished without written permission; see the terms.

Stay current

Optional changelog list — one email per major endpoint release. Not required to subscribe; the existing API works today without it.