---
title: "Probability history for one outcome of an event"
method: GET
path: "/api/prediction-markets/event/{source}/{slug}/price-history"
tags: ["public-pm-data"]
---

# Probability history for one outcome of an event

`GET /api/prediction-markets/event/{source}/{slug}/price-history`

## Request

- Base URL: `https://api.coinrithm.com`
- URL: `https://api.coinrithm.com/api/prediction-markets/event/{source}/{slug}/price-history`
- Auth: none required

Native venue price history for ONE outcome of the event: the Yes leg
of a binary market, else the first live outcome by sort order (not
resolved, voided or closed), else the first outcome. `outcome` names
it; on a multi-outcome event, use event detail for the others.

Polymarket and Kalshi only. Other venues answer 200 with `points: []`,
which means "not served here", not "no trading".

`interval` is a lookback range, not a bucket size. The venue picks
point spacing (Polymarket 1d: about one point per minute). Depth still
varies by venue: check `coverage.probabilityHistoryStartDay` on
/sources before assuming a long window exists.

## Path parameters

- `source` 'polymarket' | 'kalshi' | 'rothera' | 'limitless' | 'smarkets' | 'manifold' | 'metaculus' | 'predictit' | 'futuur' | 'myriad' | 'forecastex' | 'gemini', required
- `slug` string, required

## Query parameters

- `interval` '1h' | '6h' | '1d' | '1w' | '1m' | 'max'

## Response `200`

Probability points for one outcome, oldest first

- object
  - `source` string, required
  - `slug` string, required
  - `interval` string, required: The range served, in canonical form (1h, 6h, 1d, 1w, 1m or max).
  - `outcome` object, nullable: The outcome this series describes; null when the event has no outcomes.
    - `name` string, nullable
    - `externalMarketId` string, nullable
  - `points` object[], required
    - `t` integer, required: Unix ms
    - `p` number, required: Probability 0..1

## Other responses

- `400`: Invalid or missing parameters. On a route with a query allowlist, an undocumented query parameter returns `{"error": "unsupported_query_parameter", "message": "Unsupported query parameter: <key>. Supported: <keys>."}`.
- `404`: Resource not found. A path the API does not serve at all returns `{"error": "not_found", "message": "not_found"}` with `Cache-Control: no-store`.
- `500`: Server error

---

[API](https://skmtc.dev/coinrithm/apis/coinrithm-agent-trading-api.md) · [All operations](https://skmtc.dev/coinrithm/apis/coinrithm-agent-trading-api/llms.txt) · [OpenAPI document](https://skmtc.dev/coinrithm/apis/coinrithm-agent-trading-api/revisions/28fb59f285fe?raw)