> ## Documentation Index > Fetch the complete documentation index at: https://docs.neo.projectdiscovery.io/llms.txt > Use this file to discover all available pages before exploring further. # Buy extra credits on an active subscription > Buys additional credits for an active subscription as a one-off invoice tied to the subscription. Charges the saved card immediately and feeds the top-up bucket. Distinct from /billing/purchase (standalone purchases). ## OpenAPI ````yaml https://neo.api.projectdiscovery.io/api/openapi.json post /api/v1/billing/subscription/topup openapi: 3.1.0 info: contact: name: ProjectDiscovery url: https://neo.projectdiscovery.io description: Neo API Server - Security agent orchestration platform license: name: Apache 2.0 url: https://www.apache.org/licenses/LICENSE-2.0 title: Neo API version: 1.0.0 servers: - description: Production url: https://neo.api.projectdiscovery.io - description: Development url: https://neo.api.dev.projectdiscovery.io - description: Local development url: http://localhost:8080 security: [] tags: - description: Task execution and management name: Tasks - description: Agent listing and management name: Agents - description: Public agent directory name: Agent Directory - description: User file storage management name: Files - description: User working memory management name: Memory - description: Scheduled and recurring task management name: Schedules - description: Knowledge base and semantic search name: Knowledge - description: Encrypted user credentials and API keys name: Secrets - description: Neo API key management for programmatic access name: API Keys - description: User profile and account information name: User - description: Task and LLM usage tracking name: Usage - description: Bring Your Own Key provider management name: BYOK - description: Model discovery and capabilities name: Models - description: Third-party integrations name: Integrations - description: Skill knowledge documents for agent prompts name: Skills - description: Team management and member invitations name: Teams - description: Prompt library management and discovery name: Prompts - description: Slack bot integration for workspace installation and OAuth name: Slack - description: GitHub integration for PR reviews and repository management name: GitHub - description: Vulnerability issue tracking and management name: Issues - description: Subscription billing and plans name: Billing - description: Project management and member assignments name: Projects - description: SSH key pair generation and management for remote server access name: SSH Keys - description: Codebase structural analysis and mapping name: Codemaps - description: AI-generated codebase documentation and security analysis name: CodeWiki - description: Captured HTTP traffic query and replay name: Network Events - description: Vulnerability triage for HackerOne, GitHub, and Security Inbox name: Triage - description: >- Application-internal endpoints used by the Neo UI. Not part of the public customer API surface. name: Internal paths: /api/v1/billing/subscription/topup: post: tags: - Billing summary: Buy extra credits on an active subscription description: > Buys additional credits for an active subscription as a one-off invoice tied to the subscription. Charges the saved card immediately and feeds the top-up bucket. Distinct from /billing/purchase (standalone purchases). operationId: post-v1-billing-subscription-topup requestBody: content: application/json: schema: $ref: '#/components/schemas/BillingSubscriptionTopupRequest' required: true responses: '200': content: application/json: schema: $ref: '#/components/schemas/BillingSubscriptionTopupResponse' description: Top-up estimate or charged '400': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: Bad request '401': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: Unauthorized '500': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: Internal server error security: - BearerAuth: [] - ApiKeyAuth: [] components: schemas: BillingSubscriptionTopupRequest: properties: action: enum: - estimate - purchase type: string credits: format: double type: number payment_method_id: type: string required: - action - credits type: object BillingSubscriptionTopupResponse: properties: action: enum: - estimate - charged type: string x-enum-varnames: - BillingSubscriptionTopupResponseActionEstimate - BillingSubscriptionTopupResponseActionCharged amount_cents: type: integer amount_display: type: string credits: format: double type: number has_payment_method: type: boolean invoice_id: type: string invoice_url: type: string monthly_max: description: Maximum top-up credits purchasable per billing month for this buyer. format: double type: number monthly_remaining: description: Remaining top-up credits purchasable in the current billing month. format: double type: number new_topup_balance: format: double type: number payment_methods: items: $ref: '#/components/schemas/BillingPaymentMethod' type: array unit_price: format: double type: number required: - action type: object ErrorResponse: properties: code: description: > Stable machine-readable error code — branch on this rather than matching the human `error`/`message` strings. Domain codes include `user_spending_cap_reached`, `project_spending_cap_reached`, and `insufficient_neo_credits`; otherwise it mirrors the error kind (e.g. `forbidden`, `invalid_request`, `not_exists`, `already_exists`). example: user_spending_cap_reached type: string error: example: Bad request type: string error_id: description: Correlation id for a specific error instance, when present. type: string kind: description: Coarse error category (e.g. "forbidden request", "invalid request"). example: forbidden request type: string message: description: | Human-readable detail (the kind prefixed to the error). For display, not for branching. type: string required: - error type: object BillingPaymentMethod: properties: brand: description: Card brand (visa, mastercard, amex, etc.) type: string email: description: Account email for Link/PayPal payment methods type: string exp_month: description: Card expiration month (1-12) type: integer exp_year: description: Card expiration year type: integer id: description: Stripe Payment Method ID type: string is_default: description: Whether this is the default payment method type: boolean last4: description: Last 4 digits of the card type: string type: description: >- Payment method type (card, link, us_bank_account, sepa_debit, paypal, etc.) type: string type: object securitySchemes: BearerAuth: bearerFormat: JWT description: JWT authentication token scheme: bearer type: http ApiKeyAuth: description: Neo API key (neo_sk_* prefix) in: header name: X-Api-Key type: apiKey ````