> ## Documentation Index > Fetch the complete documentation index at: https://docs.beliefsystems.xyz/llms.txt > Use this file to discover all available pages before exploring further. # Get level history > Level history at `1h` or `1d`, oldest first, over the trailing 90-day window. `start`, `end`, and `interval` are all optional. With none supplied you get the full trailing window at `1d`. A window that reaches back past the floor is clamped, not rejected, so a chart that asked for a year still renders. `meta` reports what was actually served: `effectiveStart`, `effectiveEnd`, `clamped`, and `historyMaxDays`. Read `clamped` before labeling a chart with the range you asked for. A window falling entirely before the floor returns an empty `points` array with `clamped: true`. Full history since inception is in the free snapshot bundles. ## OpenAPI ````yaml /api-reference/openapi.json get /v1/indices/{ticker}/history openapi: 3.1.0 info: contact: name: Belief Systems url: https://beliefsystems.xyz/data description: >- Rules-based benchmark data for prediction markets: Belief index levels and Belief Volatility series, read over HTTPS with an API key. The API is read-only. Every endpoint is a `GET`, every successful response is `{ data, meta }`, and every failure is a single `error` object with a stable `code`. Keys are free and take about a minute to mint at https://beliefsystems.xyz/data. Attribution is required on anything you publish from this data: "Source: Belief Systems (beliefsystems.xyz)". Production, redistribution, and commercial use require a license (https://beliefsystems.xyz/license). license: name: Belief Systems Data License url: https://beliefsystems.xyz/license termsOfService: https://beliefsystems.xyz/terms title: Belief Systems Data API version: '1.0' servers: - description: Production. There is no separate test host; the API is read-only. url: https://api.beliefsystems.xyz security: - bearerAuth: [] - apiKeyAuth: [] tags: - description: >- Belief indices are rules-based benchmarks of how prediction markets price a defined set of events. Levels are exact decimal strings based at 100 on the index's inception date. name: Indices - description: >- Belief Volatility measures how much prediction-market probabilities are expected to move over a stated horizon, in probability points. Always name the tenor when quoting a value. name: Belief Volatility - description: >- The service index, which reports your key's live quota, and pointers to the free point-in-time snapshot bundles. name: Service paths: /v1/indices/{ticker}/history: get: tags: - Indices summary: Get level history description: >- Level history at `1h` or `1d`, oldest first, over the trailing 90-day window. `start`, `end`, and `interval` are all optional. With none supplied you get the full trailing window at `1d`. A window that reaches back past the floor is clamped, not rejected, so a chart that asked for a year still renders. `meta` reports what was actually served: `effectiveStart`, `effectiveEnd`, `clamped`, and `historyMaxDays`. Read `clamped` before labeling a chart with the range you asked for. A window falling entirely before the floor returns an empty `points` array with `clamped: true`. Full history since inception is in the free snapshot bundles. operationId: getIndexHistory parameters: - description: >- Ticker, case-insensitive. `GET /v1/indices` and `GET /v1/volatility` are the catalogs. example: CONFLICT in: path name: ticker required: true schema: type: string - description: >- Window start, ISO 8601. Optional. A start older than the trailing 90-day window is clamped, never rejected; `meta.clamped` says so. example: '2026-08-28T00:00:00Z' in: query name: start required: false schema: anyOf: - format: date-time type: string - type: 'null' - description: >- Window end, ISO 8601. Optional, defaults to now. A future end is clamped to now; only a window that is empty once clamped is an error. example: '2026-08-31T00:00:00Z' in: query name: end required: false schema: anyOf: - format: date-time type: string - type: 'null' - description: Sampling interval. Finer granularity is part of the licensed feed. example: 1d in: query name: interval required: false schema: default: 1d enum: - 1h - 1d type: string responses: '200': content: application/json: example: data: count: 4 interval: 1d points: - indexLevel: '35.15037728' stale: false t: '2026-08-28T00:04:50.602836Z' - indexLevel: '35.41478865' stale: false t: '2026-08-29T00:26:31.745989Z' - indexLevel: '35.47475770' stale: false t: '2026-08-30T00:35:30.281356Z' - indexLevel: '36.04218539' stale: false t: '2026-08-30T23:44:45.186614Z' ticker: CONFLICT meta: attribution: 'Source: Belief Systems (beliefsystems.xyz)' clamped: false effectiveEnd: '2026-08-31T00:00:00.000000Z' effectiveStart: '2026-08-28T00:00:00.000000Z' generatedAt: '2026-08-31T14:01:28.821152Z' historyMaxDays: 90 license: https://beliefsystems.xyz/license termsUrl: https://beliefsystems.xyz/terms schema: $ref: '#/components/schemas/IndexHistoryResponse' description: Success. '401': content: application/json: example: error: code: invalid_api_key docsUrl: >- https://docs.beliefsystems.xyz/api-reference/limits#invalid-api-key message: >- This endpoint requires a Data API key. Create one free at https://beliefsystems.xyz/data ; programmatic or commercial licensing is at https://beliefsystems.xyz/license. requestId: 9f2c1ad4e6b74c0f8a3d5e1b7c904a26 schema: $ref: '#/components/schemas/Error' description: Missing or unresolvable API key. '404': content: application/json: example: error: code: not_found docsUrl: >- https://docs.beliefsystems.xyz/api-reference/limits#not-found message: >- No Belief index 'NOPE'. GET /v1/indices lists the published catalog. requestId: 9f2c1ad4e6b74c0f8a3d5e1b7c904a26 schema: $ref: '#/components/schemas/Error' description: No index or volatility series matches that ticker on this surface. '422': content: application/json: example: error: code: invalid_interval docsUrl: >- https://docs.beliefsystems.xyz/api-reference/limits#invalid-interval message: >- interval must be '1h' or '1d'. Full granularity is part of the licensed feed. requestId: 9f2c1ad4e6b74c0f8a3d5e1b7c904a26 schema: $ref: '#/components/schemas/Error' description: A parameter failed validation. '429': content: application/json: example: error: code: rate_limited docsUrl: >- https://docs.beliefsystems.xyz/api-reference/limits#rate-limited message: 'Rate limit exceeded: 60 requests per minute per key.' requestId: 9f2c1ad4e6b74c0f8a3d5e1b7c904a26 schema: $ref: '#/components/schemas/Error' description: >- Rate limited. Sleep for `Retry-After` seconds, which is exact on both windows. default: content: application/json: schema: $ref: '#/components/schemas/Error' description: Error. Every /v1 failure uses this shape. x-codeSamples: - label: curl lang: curl source: >- curl -s "https://api.beliefsystems.xyz/v1/indices/CONFLICT/history?start=2026-08-28T00:00:00Z&end=2026-08-31T00:00:00Z&interval=1d" \ -H "Authorization: Bearer $BELIEF_API_KEY" - label: Python lang: python source: |- import os import requests resp = requests.get( "https://api.beliefsystems.xyz/v1/indices/CONFLICT/history?start=2026-08-28T00:00:00Z&end=2026-08-31T00:00:00Z&interval=1d", headers={"Authorization": f"Bearer {os.environ['BELIEF_API_KEY']}"}, timeout=10, ) resp.raise_for_status() payload = resp.json() print(payload["data"]) - label: JavaScript lang: javascript source: >- const res = await fetch("https://api.beliefsystems.xyz/v1/indices/CONFLICT/history?start=2026-08-28T00:00:00Z&end=2026-08-31T00:00:00Z&interval=1d", { headers: { Authorization: `Bearer ${process.env.BELIEF_API_KEY}` }, }); if (!res.ok) throw new Error(`Belief Systems API ${res.status}`); const { data, meta } = await res.json(); console.log(data); components: schemas: IndexHistoryResponse: properties: data: properties: count: description: Number of points returned. type: integer interval: description: The interval actually served. example: 1d type: string points: description: >- Oldest first. Empty with `clamped: true` when the whole window predates the free range. items: properties: indexLevel: description: >- Index level as an exact decimal STRING, not a JSON number. Parse it with a decimal type: floats lose the published precision on round-trip. type: string stale: description: True when this point rested on stale inputs. type: boolean t: description: >- Observation timestamp. UTC timestamp with microsecond precision, `Z`-suffixed. format: date-time type: string type: object type: array ticker: example: CONFLICT type: string type: object meta: properties: attribution: description: >- The attribution line required on anything you publish from this data. Reproduce it verbatim. example: 'Source: Belief Systems (beliefsystems.xyz)' type: string clamped: description: >- True when the requested start predated the free window. Read this before labeling a chart with the range you asked for. type: boolean effectiveEnd: description: The end actually served. Never later than now. format: date-time type: string effectiveStart: description: >- The start actually served, after clamping to the trailing window. format: date-time type: string generatedAt: description: >- When this response was generated. UTC timestamp with microsecond precision, `Z`-suffixed. format: date-time type: string historyMaxDays: description: The trailing window in force, in days. Currently 90. example: 90 type: integer license: description: Terms covering production, redistribution, and commercial use. format: uri type: string termsUrl: description: Terms of Service. format: uri type: string required: - attribution - license - termsUrl - generatedAt - effectiveStart - effectiveEnd - clamped - historyMaxDays type: object required: - data - meta type: object Error: description: >- Every failure replaces `data` and `meta` with a single `error` object. Match on `code`, which is a stable contract. `message` is written for a person and may be reworded. properties: error: properties: code: description: Stable machine-readable error code. enum: - invalid_api_key - ip_rate_limited - rate_limited - daily_limit_reached - not_found - invalid_parameter - invalid_interval - invalid_window - method_not_allowed - internal_error - unavailable - error type: string docsUrl: description: Deep link to this code on the limits and errors page. format: uri type: string message: description: Human-readable explanation. Not a stable contract. type: string requestId: description: >- Correlation id, also returned as the X-Request-Id header. Quote it in support requests. type: string required: - code - message - docsUrl - requestId type: object required: - error title: Error type: object securitySchemes: bearerAuth: description: >- Your Data API key as a Bearer token: `Authorization: Bearer belief_live_...`. This is the canonical form. Keys belong on a server, never in a browser. scheme: bearer type: http apiKeyAuth: description: >- The same key sent as `X-API-Key` instead. Accepted everywhere the Bearer header is. Send one or the other, not both. in: header name: X-API-Key type: apiKey ````