> ## 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. # List volatility series > The Belief Volatility catalog: every published series with its tenors, headline tenor, units, and the publication gates in force. An unlaunched surface returns an empty catalog rather than an error. ## OpenAPI ````yaml /api-reference/openapi.json get /v1/volatility 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/volatility: get: tags: - Belief Volatility summary: List volatility series description: >- The Belief Volatility catalog: every published series with its tenors, headline tenor, units, and the publication gates in force. An unlaunched surface returns an empty catalog rather than an error. operationId: listVolatilitySeries responses: '200': content: application/json: example: data: count: 1 productFamily: belief_volatility series: - category: elections definitionLine: >- Belief Volatility is a standardized estimate of how much prediction-market probabilities are expected to move over a stated horizon. description: >- How much the 2026 U.S. midterms balance-of-power distribution is expected to move. gates: arbMinDepthUsd: 500 arbToleranceMin: 0.01 arbToleranceTicks: 1 depthFloorUsd: 500 devigTolerance: 0.000001 identityTolerance: 0.000001 impactBudgetPts: 1 overroundFlagHi: 1.04 overroundFlagLo: 0.995 pythagoreanTolerancePts2: 0.01 retireAfterDegradedTicks: 12 snapshotMaxAgeSeconds: 900 snapshotMaxSkewSeconds: 300 spreadToMidMax: 0.5 suspendFailingBudgetShare: 0.1 headlineTenorDays: 30 inceptionAt: '2026-08-06T00:01:51.828235Z' listed: true methodologyUrl: https://docs.beliefsystems.xyz/volatility/methodology name: Midterms Uncertainty Index productFamily: belief_volatility relatedIndexTickers: - MIDR26 - MIDD26 settlementDate: '2027-01-05' slug: midvol targetType: partition_composite tenorsDays: - 1 - 7 - 30 ticker: MIDVOL units: probability points meta: attribution: 'Source: Belief Systems (beliefsystems.xyz)' generatedAt: '2026-08-31T14:01:22.277647Z' license: https://beliefsystems.xyz/license termsUrl: https://beliefsystems.xyz/terms schema: $ref: '#/components/schemas/VolatilityListResponse' 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. '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/volatility" \ -H "Authorization: Bearer $BELIEF_API_KEY" - label: Python lang: python source: |- import os import requests resp = requests.get( "https://api.beliefsystems.xyz/v1/volatility", 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/volatility", { 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: VolatilityListResponse: properties: data: properties: count: type: integer productFamily: example: belief_volatility type: string series: items: description: >- The series definition. Identical across the catalog, latest, and history endpoints. properties: category: example: elections type: string definitionLine: description: >- The standing definition of Belief Volatility. Quote it when publishing a value. type: string description: description: One line on what the series measures. type: string gates: additionalProperties: true description: >- The publication tolerances in force for this series: overround bounds, depth floors, spread ceilings, and any partition consistency checks. Published so a value can be checked against the gates that admitted it. Field set varies by series target type. See the Belief Volatility methodology for what each gate tests. type: object headlineTenorDays: description: >- The tenor `headlinePts` refers to. Always name the tenor when quoting a value. example: 30 type: integer inceptionAt: format: date-time type: string listed: description: True when the series is published on the public surface. type: boolean methodologyUrl: format: uri type: string name: example: Midterms Uncertainty Index type: string productFamily: example: belief_volatility type: string relatedIndexTickers: description: Belief indices covering the same underlying events. items: type: string type: array settlementDate: description: Backstop settlement date, ISO 8601 date. type: - string - 'null' slug: description: URL segment for this series on beliefsystems.xyz. type: string targetType: description: The structure being measured. example: partition_composite type: string tenorsDays: description: Horizons published for this series, in days. example: - 1 - 7 - 30 items: type: integer type: array ticker: example: MIDVOL type: string units: description: The unit every `pts` value is quoted in. example: probability points type: string type: object type: array 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 generatedAt: description: >- When this response was generated. UTC timestamp with microsecond precision, `Z`-suffixed. format: date-time type: string 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 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 ````