> ## Documentation Index > Fetch the complete documentation index at: https://commet.co/docs/llms.txt > Use this file to discover all available pages before exploring further. # Compare plan versions > List what changes from one version of a plan to the version sent in against: prices, trials, features, rules, add-ons, credit packs and countries. Each change goes from this version's value to the compared version's value. List what changes from one version of a plan to the version sent in against: prices, trials, features, rules, add-ons, credit packs and countries. Each change goes from this version's value to the compared version's value. ## OpenAPI ````yaml /openapi/es/rest/2026-08-27.json get /plans/{id}/versions/{versionId}/changes openapi: 3.1.0 info: title: Commet API version: '2026-08-27' description: Billing and payments API for SaaS and AI products. servers: - url: https://commet.co/api/v1 security: - ApiKeyAuth: [] tags: - name: Test Clock description: >- Simulate the passage of time in sandbox to test billing flows. Mirrors Stripe test clocks: forward-only and sandbox-only. - name: Customers - name: Subscriptions - name: Plans - name: Markets description: >- Reusable country groups for market-specific prices and selectable price variants. - name: Offers - name: Promo Codes - name: Features - name: Usage - name: Seats - name: Quota - name: Add-ons - name: Portal - name: Credit Packs - name: Plan Groups - name: Invoices - name: Payments description: >- One-time payments with no subscription or plan. Charge a customer's saved payment method off-session, or create a payment link the customer opens to pay. Tax, invoice, and receipt are handled automatically. - name: Transactions - name: Webhooks - name: API Keys - name: Payouts description: >- Withdraw available balance to your bank and manage the payout account (verification + destination bank accounts). - name: Provisioning description: >- Take ownership of an organization an agent provisioned headlessly. The agent holds the API keys from the start; a human claims the account through a claim link. paths: /plans/{id}/versions/{versionId}/changes: get: tags: - Plans summary: Compare plan versions description: >- List what changes from one version of a plan to another: prices, trials, features, rules, add-ons, credit packs and countries. operationId: compare-plan-versions parameters: - name: id in: path required: true schema: type: string - name: versionId in: path required: true schema: type: string - name: against in: query required: true schema: type: string description: >- The version to compare with. Each change goes from this version's value to the compared version's value. - name: Commet-Version in: header required: false description: >- API version used by this reference. Send this header to select this contract explicitly. schema: type: string default: '2026-08-27' example: '2026-08-27' responses: '200': description: Success headers: X-Request-Id: $ref: '#/components/headers/RequestId' RateLimit-Limit: description: Maximum number of requests allowed in the current window. schema: type: string RateLimit-Remaining: description: Requests remaining in the current window. schema: type: string content: application/json: schema: $ref: '#/components/schemas/PlanVersionComparison' example: versionId: plr_9i0j1k2l againstVersionId: plr_5m6n7o8p changes: - key: price:pp_1a2b3c4d section: Price country: null label: Monthly price before: $49.00 after: $59.00 - key: feature:pf_9z8y7x6w section: What's included country: null label: Agent runs before: 1,000 included after: 2,000 included '400': description: Bad request headers: X-Request-Id: $ref: '#/components/headers/RequestId' content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: type: validation_error code: validation_error message: The request contains an invalid parameter. doc_url: >- https://commet.co/docs/api-reference/2026-08-27/errors/validation_error.md '401': description: Unauthorized headers: X-Request-Id: $ref: '#/components/headers/RequestId' content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: type: authentication_error code: unauthorized message: A valid API key is required. doc_url: >- https://commet.co/docs/api-reference/2026-08-27/errors/unauthorized.md '403': description: Forbidden headers: X-Request-Id: $ref: '#/components/headers/RequestId' content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: type: authentication_error code: forbidden message: You do not have permission to perform this operation. doc_url: >- https://commet.co/docs/api-reference/2026-08-27/errors/forbidden.md '404': description: Not found headers: X-Request-Id: $ref: '#/components/headers/RequestId' content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: type: not_found_error code: not_found message: The requested resource was not found. doc_url: >- https://commet.co/docs/api-reference/2026-08-27/errors/not_found.md '429': description: Too many requests headers: X-Request-Id: $ref: '#/components/headers/RequestId' RateLimit-Limit: description: Maximum number of requests allowed in the current window. schema: type: string RateLimit-Remaining: description: Requests remaining in the current window. schema: type: string RateLimit-Reset: description: Seconds until the rate limit window resets. schema: type: string Retry-After: description: Seconds to wait before retrying the request. schema: type: string content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: type: rate_limit_error code: rate_limited message: >- Too many requests. Retry after the interval specified in the Retry-After header. doc_url: >- https://commet.co/docs/api-reference/2026-08-27/errors/rate_limited.md '500': description: Internal server error headers: X-Request-Id: $ref: '#/components/headers/RequestId' content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: type: internal_error code: internal_error message: An unexpected error occurred while processing the request. doc_url: >- https://commet.co/docs/api-reference/2026-08-27/errors/internal_error.md components: headers: RequestId: description: >- Server-generated identifier that correlates this response with Platform logs. schema: type: string format: uuid schemas: PlanVersionComparison: type: object properties: versionId: type: string description: The version the changes start from. againstVersionId: type: string description: The version they end at. changes: type: array items: type: object properties: key: type: string description: Identifies the change; send it to undo just this change. section: type: string description: >- Where the change is: Price, Trial, a rules section, Add-ons, or a country. country: description: ISO country code when the change belongs to one country. type: - string - 'null' label: type: string description: What changed, such as Monthly price. before: description: The value before, formatted. type: - string - 'null' after: description: The value now, formatted. type: - string - 'null' required: - key - section - country - label - before - after additionalProperties: false description: Every term that differs, the plan's first and then each country. object: type: string const: plan_version_comparison livemode: type: boolean required: - versionId - againstVersionId - changes - object - livemode additionalProperties: false ErrorResponse: type: object properties: error: type: object properties: type: type: string code: type: string message: type: string param: type: string details: {} doc_url: type: string required: - type - code - message - doc_url additionalProperties: false required: - error additionalProperties: false securitySchemes: ApiKeyAuth: type: apiKey in: header name: x-api-key ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.