> ## Documentation Index > Fetch the complete documentation index at: https://docs.nozle.dev/llms.txt > Use this file to discover all available pages before exploring further. # The credits of a paid top up can be spent > The Engine granted the credits of a paid top-up purchase, so they are in the customer's balance and can be spent. Sent once per purchase, after the grant is committed. A paid invoice alone does not mean the credits are spendable; wait for this event or poll `GET /credit-top-up-purchases/{id}` until `fulfillment_status` is `fulfilled`. ## OpenAPI ````yaml /nozle-openapi.yaml webhook credit_top_up_purchase_fulfilled openapi: 3.1.0 info: title: Nozle API description: >- One specification for the Nozle API. Core operations use the default server https://api.nozle.app/core/api/v1. Engine operations name their own server, https://api.nozle.app/engine/api/v1. Both live on the one host https://api.nozle.app. **Legacy key names, removed in Core 6.0.0.** REST responses, webhook payloads and CSV exports carry only the Nozle names: `nozle_id` and the plain `` names such as `customer_id` and `invoice_id`. The former-prefix keys, the former EU tax codes, the former CSV id columns and the former webhook headers are gone. Webhook deliveries carry `X-Nozle-Signature`, `X-Nozle-Signature-Algorithm` and `X-Nozle-Unique-Key`. nozle-js and nozle-python older than 0.10.0 and nozle-go older than 0.9.1 cannot read a credit system id from Core 6.0.0. version: 1.50.0 license: name: AGPLv3 url: https://github.com/nozle-dev/core/blob/main/LICENSE contact: email: support@nozle.app servers: - url: https://api.nozle.app/core/api/v1 description: Nozle Billing API security: - bearerAuth: [] tags: - name: Activity Logs description: Everything about Activity logs externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Analytics description: Everything about Analytics - name: API Logs description: Everything about API logs externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Features description: Everything about Feature collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Entitlements description: Everything about Entitlement collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Billing Entities description: Everything about Billing Entities externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Customers description: Everything about Customer collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Plans description: Everything about Plan collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Subscriptions description: Everything about Subscription collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Events description: Everything about Event collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Cost Events description: Detailed internal cost usage linked to Feature Events or customers - name: Shared Costs description: Preview and finalize allocated period costs - name: Cost Intelligence description: Ledger-backed cost analytics and profitability inputs - name: Organizations description: Everything about Organization collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Taxes description: Everything about Tax collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Coupons description: Everything about Coupon collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Add-ons description: Everything about Add-on collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Fees description: Everything about Fees externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Invoices description: Everything about Invoice collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Wallets description: Everything about Wallet collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Credit Notes description: Everything about Credit notes collection externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Webhooks description: Everything about Webhooks externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Webhook Endpoints description: Everything about Webhook Endpoints externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Payment Receipts description: Everything about Payment receipts externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Payment Requests description: Everything about PaymentRequests externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Payments description: Everything about Payments externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Payment Methods description: Everything about Payment Methods externalDocs: description: Find out more url: https://docs.nozle.dev/api-reference - name: Billing Imports description: Billing Imports operations - name: Billing Status description: Billing Status operations - name: Checkout description: Checkout operations - name: Cost Models description: Cost Models operations - name: Credit Imports description: Credit Imports operations - name: Credits description: Credits operations - name: Entities description: Entities operations - name: Entity Subscriptions description: Entity Subscriptions operations - name: Health description: Health operations - name: LLM Proxy description: LLM Proxy operations - name: Margin description: Margin operations - name: Subscription Changes description: Subscription Changes operations - name: Usage description: Usage operations externalDocs: description: Nozle Github url: https://github.com/nozle-dev paths: {} components: securitySchemes: bearerAuth: type: http scheme: bearer ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.