> ## Documentation Index > Fetch the complete documentation index at: https://docs.paygentic.io/llms.txt > Use this file to discover all available pages before exploring further. # Purchase Grant > Create an ad-hoc invoice with a payment session for a grant purchase. The customer pays via the returned payment URL; the grant is created automatically on payment completion. If payment expires, the invoice is cancelled and no grant is created. To confirm payment completion, subscribe to the `invoice.paid.v0` webhook. The payload includes the original `invoiceId` and the created `grantId`, so you can correlate the purchase response with downstream fulfilment without an extra fetch. As a fallback if you cannot consume webhooks, poll `GET /v2/invoices/{invoiceId}` (interval 2s, timeout 60s) and check for `status === "PAID"`. ## OpenAPI ````yaml /openapi.json post /v1/entitlements/{entitlementId}/grants/purchase openapi: 3.1.0 info: title: Paygentic API version: 0.1.0 description: > The Paygentic API provides a comprehensive platform for building and scaling monetization infrastructure. ## Authentication All API requests require authentication using an API key passed in the `Authorization` header: ``` Authorization: Bearer YOUR_API_KEY ``` ## Base URL All API requests should be made to: ``` https://api.paygentic.io/v0 ``` contact: name: Paygentic Support email: support@paygentic.io license: name: Proprietary servers: - url: https://api.paygentic.io description: Production API - url: https://api.sandbox.paygentic.io description: Sandbox API security: - BearerAuth: [] tags: - name: Customers description: >- A `Customer` is an entity connected to a `Merchant` via a `Subscription`. This represents the merchant-facing perspective of `Consumers` who purchase their `Products`. - name: Billable Metrics description: >- A `Billable Metric` defines a measurable quantity tied to a `Product`'s consumption. Each metric stores details including its label, an explanatory description, and measurement units. - name: Grants description: >- Grants credit a customer's metered entitlement balance. Merchants can create grants directly or void existing ones. Use `GET /v1/entitlements?customerId={id}` or `GET /v1/entitlements?subscriptionId={id}` to find the metered entitlement `id` needed for these endpoints. - name: Features description: >- A `Feature` represents a specific capability or functionality provided by a `Product`. Features can be metered (usage-based), static (fixed allocation), or boolean (enabled/disabled). - name: Fees description: >- A `Fee` defines a recurring or one-time charge tied to a `Product`. Fees are linked to prices, and cadence is defined on the Price. - name: Plans description: >- A `Plan` links a collection of `Prices` to a `Product`. It functions as a pricing structure document for a particular feature set or service offering. - name: Prices description: >- A `Price` determines the monetary value for a single unit of a `Billable Metric`. Prices are exclusively grouped within a `Plan`. - name: Products description: >- A `Product` is an offering sold by a `Merchant`. It includes product metadata like title, summary, and pricing details. `Plans`, `Prices`, and `Subscriptions` are all associated with products. - name: Sources description: >- A `Source` is an external data provider capable of automatically creating usage events. Configuration occurs at the plan level, enabling data retrieval from third-party platforms such as Stripe to produce billable events. - name: Subscriptions description: >- A `Subscription` is a customer's commitment to purchase a `Product` following the terms of a `Plan` and its linked `Prices`. - name: Users description: >- A `User` is an entity granted access to an Organization's resources. All operations are performed by users. - name: Invoices V2 description: >- Invoice V2 operations supporting billing cycles organized by time periods. Warning: v0 invoice endpoints are no longer supported. - name: Revenue description: Revenue data from invoices and payments - name: Profitability description: Per-customer profitability summaries - name: Test Clocks description: >- Test clocks provide programmable time control to simulate subscription and billing scenarios during testing. - name: Events description: Ingest raw metering events that are processed by the meters service. - name: Payments description: >- Create and manage one-off payments. A payment represents a single charge that a merchant wants to collect from a customer. - name: Payment Sessions description: >- Handle payment session lifecycle and processing across various entity types including invoices and subscriptions - name: Costs description: >- A Cost represents the operational or infrastructure expense of serving customers for a given product. Costs are metered (driven by event-based usage) and are tracked in parallel with billable metrics to give merchants visibility into both revenue and cost per customer. - name: ExternalReferences description: >- An `ExternalReference` links a Paygentic entity (e.g. an `Item`) to a record in an external system such as Salesforce or NetSuite. Multiple external records may map to the same Paygentic entity, but each external id is the *primary* reference of at most one entity per merchant. - name: Items description: >- An `Item` is the canonical "thing you sell" that external-system mappings point at. It is fully decoupled from the billing `Product` and holds no pricing/plan/metering, and it is CRM/ERP agnostic — which providers map to it lives entirely in its `ExternalReference` rows. - name: MerchantIntegrations description: >- A `MerchantIntegration` records a merchant's connection to an external provider. One connection per `(merchant, provider)` — re-connecting upserts in place. - name: Approvals description: Submit, decide, cancel, and read maker-checker approvals. - name: Orders description: Manage Orders, their line items, and billing schedules. - name: Billing Schedules description: >- Owner-polymorphic billing schedules with intervals and staged invoice projections. A BillingSchedule belongs to exactly one Order or one Subscription (XOR). Cadence lives on ScheduleIntervals (cadence-on-the-line). paths: /v1/entitlements/{entitlementId}/grants/purchase: parameters: - name: entitlementId in: path required: true description: The unique identifier of the entitlement schema: type: string pattern: ^ent_[a-zA-Z0-9]+$ post: tags: - Grants summary: Purchase Grant description: >- Create an ad-hoc invoice with a payment session for a grant purchase. The customer pays via the returned payment URL; the grant is created automatically on payment completion. If payment expires, the invoice is cancelled and no grant is created. To confirm payment completion, subscribe to the `invoice.paid.v0` webhook. The payload includes the original `invoiceId` and the created `grantId`, so you can correlate the purchase response with downstream fulfilment without an extra fetch. As a fallback if you cannot consume webhooks, poll `GET /v2/invoices/{invoiceId}` (interval 2s, timeout 60s) and check for `status === "PAID"`. operationId: purchaseEntitlementGrant parameters: - name: entitlementId in: path required: true schema: type: string pattern: ^ent_[a-zA-Z0-9]+$ description: The unique identifier of the entitlement to purchase credits for. requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/PurchaseGrantRequest' examples: basic: summary: Basic grant purchase description: Purchase 1000 credits for $5.00 with a unique idempotency key. value: amount: 1000 price: '5.00' idempotencyKey: purchase-march-2026-topup withOptions: summary: Grant purchase with all options description: >- Purchase with redirect URLs, payment expiry, and grant expiration. value: amount: 500 price: '2.50' idempotencyKey: purchase-promo-500 effectiveAt: '2026-03-14T00:00:00Z' expiresAt: '2026-04-14T00:00:00Z' successUrl: https://example.com/success cancelUrl: https://example.com/cancel paymentExpiresAt: '2026-03-15T00:00:00Z' responses: '201': description: Grant purchase invoice created with payment session. content: application/json: schema: $ref: '#/components/schemas/PurchaseGrantResponse' '400': $ref: '#/components/responses/BadRequest' '403': $ref: '#/components/responses/Forbidden' '404': $ref: '#/components/responses/NotFound' '409': $ref: '#/components/responses/Conflict' '500': $ref: '#/components/responses/InternalServerError' components: schemas: PurchaseGrantRequest: type: object required: - amount - price - idempotencyKey properties: amount: type: number exclusiveMinimum: 0 exclusiveMaximum: 1000000000000 multipleOf: 1.e-8 description: The number of credits to grant upon payment completion. price: type: string pattern: ^\d+(\.\d{1,9})?$ description: >- The price in decimal format (e.g., '5.00' for $5.00 USD). A non-negative decimal with at most 9 fractional digits (nanodollar precision). Must be at least $0.50 and must not exceed 4503599.62 (the maximum supported grant purchase amount). idempotencyKey: type: string minLength: 1 maxLength: 255 description: >- Caller-provided deduplication key. Retrying with the same key returns the existing invoice. effectiveAt: type: string format: date-time description: When the grant becomes effective. Defaults to now. expiresAt: type: string format: date-time nullable: true description: When the grant expires. If omitted, the grant does not expire. successUrl: type: string format: uri description: URL to redirect the customer to after successful payment. cancelUrl: type: string format: uri description: URL to redirect the customer to if payment is cancelled. paymentExpiresAt: type: string format: date-time description: >- When the payment session expires. If omitted, uses the default expiry. resetMaxRollover: type: number minimum: 0 maximum: 999999999999 description: >- Maximum balance carried over at the entitlement's reset boundary. If omitted, the purchased grant balance rolls over until consumed or expired. Set to 0 to discard any remaining balance at each reset. Ignored when the target entitlement has no `usagePeriod` (one-time entitlement) — one-time entitlements have no reset boundary, so this field has no effect. resetMinRollover: type: number minimum: 0 maximum: 999999999999 description: >- Minimum balance at the entitlement's reset boundary; balances below this are floored up. Defaults to 0 (no floor). Ignored when the target entitlement has no `usagePeriod` (one-time entitlement). PurchaseGrantResponse: type: object required: - object - invoiceId - entitlementId - grantAmount - price - currency - paymentSessions properties: object: type: string enum: - grant_purchase default: grant_purchase invoiceId: type: string pattern: ^inv_[a-f0-9]+$ description: The invoice ID for this grant purchase. entitlementId: type: string pattern: ^ent_[a-zA-Z0-9]+$ description: The entitlement that will receive the grant. grantAmount: type: number exclusiveMinimum: 0 description: The number of credits that will be granted on payment. price: type: string description: The price in decimal format (e.g., '5.00'). currency: type: string description: The three-letter ISO 4217 currency code (e.g., 'usd'). paymentSessions: type: array items: type: object required: - url properties: url: type: string format: uri description: The Stripe checkout URL for the customer to complete payment. expiresAt: type: string format: date-time nullable: true description: When the payment session expires. amount: type: number description: The payment amount in the currency's minor unit (e.g., cents). description: Payment session(s) for the customer to complete the purchase. Error: type: object required: - message properties: error: type: string description: >- Coarse HTTP error category (e.g. 'bad_request', 'forbidden'). Maps to the HTTP status code. message: type: string description: >- Human-readable error message. Clients must not parse this field programmatically. code: type: string examples: - TAX_NOT_ENABLED - PAYMENT_SESSION_EXPIRED description: >- Optional semantic business error code for machine-readable discrimination (e.g. 'TAX_NOT_ENABLED'). UPPER_SNAKE_CASE. Clients should check this field, not message. details: type: object description: Additional error details additionalProperties: true example: message: The requested resource was not found error: not_found ValidationError: type: object required: - message - errors properties: error: type: string enum: - validation_error default: validation_error description: Error type indicating validation failure message: type: string description: Human-readable error message errors: type: array items: type: object properties: field: type: string description: The field that failed validation message: type: string description: Validation error message for this field code: type: string description: Validation error code required: - field - message description: Array of field-specific validation errors example: message: Validation failed error: validation_error errors: - field: email message: Invalid email format code: invalid_format responses: BadRequest: description: >- Bad Request - The request could not be understood or was missing required parameters content: application/json: schema: oneOf: - $ref: '#/components/schemas/Error' - $ref: '#/components/schemas/ValidationError' Forbidden: description: Forbidden - Request is understood but refused content: application/json: schema: $ref: '#/components/schemas/Error' NotFound: description: Not Found - The requested resource could not be found content: application/json: schema: $ref: '#/components/schemas/Error' Conflict: description: Conflict - The request conflicts with the current state of the resource content: application/json: schema: $ref: '#/components/schemas/Error' InternalServerError: description: Internal Server Error - Something went wrong on the server side content: application/json: schema: $ref: '#/components/schemas/Error' securitySchemes: BearerAuth: type: http scheme: bearer description: API key authentication ````