Credence

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One endpoint family. One probability object.

Credence is an HTTPS JSON API (and an MCP server). Reference a market — by id, slug, URL, or token — and get back a probability object: the market’s price, our calibrated probability, evidence strength (n_effective), and the full Beta distribution, each response stamped with audit-grade lineage.

Access is gated to design partners and early-access developers today.

Authentication

Every request carries your key as a bearer token:

Authorization: Bearer cpk_...

Keys are issued to design partners and early-access developers — request one below. A missing or bad key returns 401 invalid_api_key.

Your first call

Resolve a market and read its probability object — the same call in curl and Python.

curl
curl -s -G "https://api.credence.at/v1/probabilities/dems-control-senate-2026" \
  --data-urlencode "ref=slug" \
  --data-urlencode "include=distribution" \
  -H "Authorization: Bearer cpk_..."
python
import requests

r = requests.get(
    "https://api.credence.at/v1/probabilities/dems-control-senate-2026",
    params={"ref": "slug", "include": "distribution"},
    headers={"Authorization": "Bearer cpk_..."},
)
print(r.json()["probability"])

The response

{
  "request_id": "req_01jw9t6c0fz8m4q2r7v3k5b9xn",
  "snapshot": {
    "snapshot_id": "api-forecast-20260525T141200Z",
    "as_of": "2026-05-25T14:12:00Z",
    "freshness_sec": 9,
    "release_id": "rel_2026_05_25_141200",
    "model_version": "research-20260503T151421Z",
    "methodology_version": "b7e2a019c4f3d586",
    "market_count": 54187
  },
  "probability": {
    "request": {
      "input": "dems-control-senate-2026",
      "resolved_market_id": "0x..."
    },
    "p_market": 0.46,
    "p_calibrated": 0.54,
    "n_effective": 12.9,
    "distribution": {
      "family": "beta",
      "alpha": 6.966,
      "beta": 5.934
    }
  }
}

What comes back

  • request_id — unique id for this request.
  • snapshot — the immutable snapshot the answer came from: snapshot_id, as_of, freshness_sec, release_id, model_version, methodology_version, market_count.
  • probability — request (your input + resolved_market_id), p_market, p_calibrated, n_effective, and (with include=distribution) distribution = { family: "beta", alpha, beta }.

Invariants you can rely on

  • p_market in [0,1]
  • p_calibrated in (0,1)
  • n_effective > 0
  • alpha = p_calibrated × n_effective
  • beta = (1 − p_calibrated) × n_effective

What the numbers mean

Endpoints

  • GET /v1/probabilities/{ref} — single lookup. ref resolves by market_id (default), token_id, slug, or url; add ?include=distribution.
  • POST /v1/probabilities/query — batch lookup, up to 100 references in one call.
  • GET /v1/snapshots/current — current snapshot metadata (freshness, versions).
  • GET /v1/snapshots/{id}/probabilities — a retained snapshot’s probabilities, paged by cursor. Replay any past snapshot, by id.
  • GET /v1/markets — search and resolve markets.

Errors & rate limits

Standard HTTP status codes with a stable machine code in the body:

  • 400 invalid_request
  • 401 invalid_api_key
  • 404 market_not_found
  • 429 rate_limited (back off per the Retry-After header)
  • 503 temporarily_unavailable

Snapshot routes can also return snapshot_not_found / snapshot_expired. Requests are rate-limited per key; limits depend on your plan.

MCP-native

Credence also runs as an MCP server, so an agent calls it as native tools inside its own loop — no glue code:

  • get_probability — one market
  • query_probabilities — up to 100
  • search_markets — find the market

Same probability object as REST. Available to design partners today.

Request access

API keys and MCP server access are issued to design partners and early-access developers ahead of public launch.

Early access See the product Read the methodology