> ## Documentation Index > Fetch the complete documentation index at: https://docs.app.strix.ai/llms.txt > Use this file to discover all available pages before exploring further. # Buy credits with a machine payment > Buy scan credits with the Machine Payments Protocol (MPP). Authenticate with `X-Strix-Authorization: Bearer ` because MPP uses the standard Authorization header for its payment credential. The first request without a payment credential returns HTTP 402 with a payment challenge. Pay the challenge with a Stripe agent wallet (https://link.com/agents), then retry the request with the payment credential. The user approves each payment in the Link app. If the user does not want a wallet, create a hosted checkout link with the billing checkout operation instead. A verified payment grants the credits one time and returns a receipt. Requires the billing:write scope and the admin role. ## OpenAPI ````yaml /openapi.json post /billing/topup openapi: 3.1.0 info: title: Strix API version: 1.0.0 description: >- Public REST API for the Strix autonomous penetration testing platform. Manage scans, vulnerabilities, assets, schedules, API tokens, and webhooks. servers: - url: /api/v1 description: Strix v1 API security: - BearerAuth: [] tags: - name: Scans description: Launch, monitor, and manage security scans. - name: Vulnerabilities description: View and triage discovered vulnerabilities. - name: Assets description: Domains and repositories registered for scanning. - name: Schedules description: Recurring scan schedules (Pro plan). - name: Tokens description: Manage API tokens for authentication. - name: Webhooks description: Configure webhook subscriptions for real-time event notifications. - name: Organization description: Workspace configuration for the authenticated organization. - name: Members description: Manage organization members and roles. - name: Invitations description: List and revoke organization invitations. - name: PR Reviews description: Automated security review of pull requests. - name: Connectors description: Network connectors for scanning internal/private targets. - name: Knowledge description: >- Organization knowledge base: documents, policies, and repo profiles that steer the agent. - name: Uploads description: Upload source/code/documentation archives for whitebox scans. - name: Integrations description: Third-party integrations (GitLab, Bitbucket, ticketing). - name: Chat description: Conversational agent sessions. - name: Analytics description: Aggregate dashboard analytics. - name: Test Users description: >- Per-domain test accounts (with optional MFA) the agent authenticates as during scans. - name: License description: Self-hosted license state, entitlements, and aggregate usage. - name: Supply Chain description: >- SBOM inventory, supply-chain findings, scans, and policy for connected repositories. - name: CLI description: >- Device authorization endpoints that let the Strix CLI and coding agents sign in and receive an API token. - name: Billing description: Credit balance, agent-payable top-ups, and automatic top-up settings. - name: Workspaces description: List, create, and switch workspaces. paths: /billing/topup: post: tags: - Billing summary: Buy credits with a machine payment description: >- Buy scan credits with the Machine Payments Protocol (MPP). Authenticate with `X-Strix-Authorization: Bearer ` because MPP uses the standard Authorization header for its payment credential. The first request without a payment credential returns HTTP 402 with a payment challenge. Pay the challenge with a Stripe agent wallet (https://link.com/agents), then retry the request with the payment credential. The user approves each payment in the Link app. If the user does not want a wallet, create a hosted checkout link with the billing checkout operation instead. A verified payment grants the credits one time and returns a receipt. Requires the billing:write scope and the admin role. operationId: purchaseCredits requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/TopupRequest' responses: '200': description: Payment verified and credits granted. content: application/json: schema: $ref: '#/components/schemas/TopupResult' '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '402': description: >- Payment required. The WWW-Authenticate header contains the MPP payment challenge. The body includes a wallet_setup field with instructions for wallet setup and the hosted checkout fallback. '403': $ref: '#/components/responses/Forbidden' '503': $ref: '#/components/responses/ServiceUnavailable' security: - StrixAuthorization: - billing:write components: schemas: TopupRequest: type: object properties: credits: type: integer minimum: 1 maximum: 10000 description: Number of credits to purchase. required: - credits TopupResult: type: object properties: credits_granted: type: integer description: >- Credits granted by this payment. Zero when the payment was already processed. duplicate: type: boolean description: True when this payment reference was already granted. reference: type: string description: Payment reference from the payment receipt. balance: type: integer description: Credit balance after the grant. required: - credits_granted - duplicate - reference - balance ErrorResponse: type: object properties: detail: type: string description: Human-readable explanation of the error. code: type: string description: >- Stable machine-readable error code. `insufficient_scope` means the token does not hold the scope that this endpoint requires. required_scope: $ref: '#/components/schemas/ApiV1Scope' description: >- Scope that the caller must add to the token. Returned with the `insufficient_scope` code. docs: type: string format: uri description: Documentation page that explains how to resolve the error. required: - detail ApiV1Scope: type: string enum: - scans:read - scans:write - vulnerabilities:read - vulnerabilities:write - dependencies:read - schedules:read - schedules:write - assets:read - assets:write - organizations:read - organizations:write - members:read - members:write - invitations:read - invitations:write - webhooks:read - webhooks:write - tokens:write - audit:read - pr_reviews:read - pr_reviews:write - connectors:read - connectors:write - knowledge:read - knowledge:write - uploads:write - integrations:read - integrations:write - chat:read - chat:write - scans:message - analytics:read - llm:read - llm:write - test_users:read - test_users:write - license:read - supply_chain:read - supply_chain:write - billing:read - billing:write responses: BadRequest: description: Bad request. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' Unauthorized: description: Missing or invalid API token. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' Forbidden: description: >- Insufficient permissions or missing scope. A missing scope returns the `insufficient_scope` code and the `required_scope` field, so a client can request the correct scope and retry. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' ServiceUnavailable: description: Service unavailable. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' securitySchemes: BearerAuth: type: http scheme: bearer description: >- API token obtained from the Tokens endpoint or CLI device login. Include as `Authorization: Bearer `. Requests made with a managed CLI session also include `X-Strix-Workspace: ` to pin a process to the workspace it started in; recovery endpoints report the current workspace after a concurrent switch. StrixAuthorization: type: apiKey in: header name: X-Strix-Authorization description: >- API token for operations where the standard Authorization header carries a protocol credential. Include as `X-Strix-Authorization: Bearer `. ````