> ## Documentation Index > Fetch the complete documentation index at: https://docs.xerobi.com/llms.txt > Use this file to discover all available pages before exploring further. # Attach Payment Method to Payment Intent > Attach an existing payment method (or ephemeral) to an intent. Idempotent by Idempotency-Key. ## OpenAPI ````yaml POST /payment_intents/{id}/attach openapi: 3.1.0 info: title: Xerobi Payment API version: '2026-01-01' description: >- A developer-first REST API for a modern payment gateway. Focused on predictable semantics, idempotency, clear errors, and observability. Use `Authorization: Bearer ` for requests. All amounts are smallest currency unit (e.g. paisa for BDT). termsOfService: https://api.hixbe.com/terms contact: name: Xerobi Developer Support url: https://developer.hixbe.com email: support@xerobi.com license: name: Proprietary url: https://hixbe.com/license servers: - url: https://sandbox.api.hixbe.com/payment description: Sandbox (test) - url: https://api.hixbe.com/payment description: Production security: - bearerAuth: [] tags: - name: PaymentIntents description: Orchestrate payments (recommended pattern) - name: PaymentMethods description: Create and manage payment methods / tokens - name: Customers description: Customer objects and stored methods - name: Refunds description: Issue partial/full refunds - name: Webhooks description: Register webhook endpoints and view events - name: Observability description: Request debugging and headers externalDocs: description: Developer guides & examples url: https://developer.hixbe.com/docs paths: /payment_intents/{id}/attach: post: tags: - PaymentIntents summary: Attach a Payment Method to a PaymentIntent description: >- Attach an existing payment method (or ephemeral) to an intent. Idempotent by Idempotency-Key. operationId: attachPaymentMethodToIntent parameters: - $ref: '#/components/parameters/Xerobi-Version' - name: id in: path required: true schema: type: string - $ref: '#/components/parameters/Idempotency-Key' requestBody: required: true content: application/json: schema: type: object properties: payment_method: type: string save_to_customer: type: boolean description: >- If true and customer provided, save as default payment method required: - payment_method example: payment_method: pm_card_123 save_to_customer: true responses: '200': description: Updated PaymentIntent content: application/json: schema: $ref: '#/components/schemas/PaymentIntent' '400': $ref: '#/components/responses/GenericError' '401': $ref: '#/components/responses/Unauthorized' components: parameters: Xerobi-Version: name: Xerobi-Version in: header description: API version header. Use '2026-01-01' for the latest version. required: true schema: type: string default: '2026-01-01' Idempotency-Key: name: Idempotency-Key in: header description: Idempotency key for safely retrying POST requests. required: false schema: type: string schemas: PaymentIntent: type: object description: >- Represents an intent to collect payment from a customer. Use confirm to finalize. properties: id: type: string example: pi_1Hh1X2AbCdEf object: type: string example: payment_intent amount: type: integer description: Amount in smallest currency unit example: 1500 currency: type: string example: BDT status: type: string enum: - requires_payment_method - requires_confirmation - processing - succeeded - requires_action - canceled example: requires_payment_method capture_method: type: string enum: - automatic - manual example: automatic client_secret: type: string description: Client-side secret used by frontends example: cs_test_abc customer: type: string nullable: true example: cus_123 payment_method: type: string nullable: true example: pm_card_abc metadata: type: object additionalProperties: type: string created_at: type: string format: date-time updated_at: type: string format: date-time charges: type: array items: $ref: '#/components/schemas/Charge' required: - id - amount - currency - status - client_secret Charge: type: object description: Represents an actual charge produced when a payment succeeds. properties: id: type: string example: ch_1Hh2Z3AbCdEf amount: type: integer example: 1500 currency: type: string example: BDT status: type: string enum: - pending - succeeded - failed - refunded example: succeeded payment_method: type: string receipt_url: type: string format: uri created_at: type: string format: date-time required: - id - amount - currency - status Error: type: object properties: error: type: object properties: type: type: string description: >- category (invalid_request, auth_error, processing_error, rate_limit, internal_error) code: type: string description: machine-friendly error code message: type: string description: human-friendly message param: type: string nullable: true description: request parameter related to the error, if any request_id: type: string description: gateway generated request id for debugging required: - type - code - message responses: GenericError: description: Standard error response content: application/json: schema: $ref: '#/components/schemas/Error' Unauthorized: description: Authentication failed content: application/json: schema: $ref: '#/components/schemas/Error' securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: JWT description: 'Use your secret API key. Example: `Authorization: Bearer sk_test_xxx`' ```` ## Related topics - [Xerobi Payment API Introduction](https://docs.xerobi.com/payment-api/introduction.md) - [Attach Payment Method to Customer](https://docs.xerobi.com/payment-api/endpoint/attach-payment-method-to-customer.md) - [Confirm Payment Intent](https://docs.xerobi.com/payment-api/endpoint/confirm-payment-intent.md) - [List Payment Intents](https://docs.xerobi.com/payment-api/endpoint/list-payment-intents.md) - [Create Payment Intent](https://docs.xerobi.com/payment-api/endpoint/create-payment-intent.md) This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.