> ## Documentation Index > Fetch the complete documentation index at: https://docs.knotapi.com/llms.txt > Use this file to discover all available pages before exploring further. # Switch Card > Switch a card in a user's merchant account. ## OpenAPI ````yaml /api-reference/openapi_secure.json POST /card openapi: 3.1.0 info: title: Knot API description: An API to interact with the Knot merchant connectivity platform. version: 1.0.0 servers: - url: https://secure.development.knotapi.com description: Development server security: - basicAuth: [] paths: /card: post: description: Switch a card in a user's merchant account. operationId: card_switch requestBody: description: The input parameters required for switching a card. content: application/json: schema: oneOf: - title: CardSwitcher type: object properties: user: type: object description: '' properties: name: type: object description: '' properties: first_name: type: string maxLength: 255 description: User's first name. example: Ada last_name: type: string maxLength: 255 description: User's last name. example: Lovelace required: - first_name - last_name phone_number: type: string description: User's phone number in E.164 format. example: '+11234567890' address: type: object description: '' properties: street: type: string maxLength: 46 description: First line of the user's billing address. example: 100 Main Street street2: type: string maxLength: 46 description: >- Second line of the user's billing address (e.g apt. #). example: '#100' city: type: string maxLength: 32 description: City portion of the user's billing address. example: New York region: type: string description: >- Region portion of the user's billing address, usually a state abbreviation. Must be an ISO 3166-2 sub-division code. example: NY postal_code: type: string maxLength: 10 minLength: 5 description: Postal code of the user's billing address. example: '12345' country: type: string description: >- Country portion of the user's billing address. Must be an ISO 3166-1 alpha-2 code. example: US required: - street - city - region - postal_code - country required: - name - phone_number - address card: type: object description: '' properties: number: type: string description: User's valid card number without spaces or hyphens. example: '4242424242424242' expiration: type: string description: >- User's card expiration date. Must be MM/YYYY or MM/YY format (e.g. 08/2027). example: 08/2025 cvv: type: string maxLength: 4 description: User's card verification value. example: '123' required: - number - expiration - cvv task_id: type: string description: >- `task_id` value provided in the [`AUTHENTICATED`](/link/webhook-events/authenticated) webhook. example: '123456' required: - user - card - task_id - title: CardUpdater type: object properties: user: type: object description: '' properties: name: type: object description: '' properties: first_name: type: string maxLength: 255 description: User's first name. example: Ada last_name: type: string maxLength: 255 description: User's last name. example: Lovelace required: - first_name - last_name phone_number: type: string description: User's phone number in E.164 format. example: '+11234567890' address: type: object description: '' properties: street: type: string maxLength: 46 description: First line of the user's billing address. example: 100 Main Street street2: type: string maxLength: 46 description: >- Second line of the user's billing address (e.g apt. #). example: '#100' city: type: string maxLength: 32 description: City portion of the user's billing address. example: New York region: type: string description: >- Region portion of the user's billing address, usually a state abbreviation. Must be an ISO 3166-2 sub-division code. example: NY postal_code: type: string maxLength: 10 minLength: 5 description: Postal code of the user's billing address. example: '12345' country: type: string description: >- Country portion of the user's billing address. Must be an ISO 3166-1 alpha-2 code. example: US required: - street - city - region - postal_code - country required: - name - phone_number - address card: type: object description: '' properties: number: type: string description: User's valid card number without spaces or hyphens. example: '4242424242424242' expiration: type: string description: >- User's card expiration date. Must be MM/YYYY or MM/YY format (e.g. 08/2027). example: 08/2025 cvv: type: string maxLength: 4 description: User's card verification value. example: '123' required: - number - expiration - cvv external_user_id: type: string description: Your unique identifier for the user. example: abc123 merchant_id: type: integer description: Unique identifier for the merchant. example: 46 card_name: type: string description: >- Name of the card. Learn more [here](/sdk/ios#customerconfiguration). example: My Credit Card customer_name: type: string description: >- Name of the customer. Learn more [here](/sdk/ios#customerconfiguration). example: John Doe required: - user - card - external_user_id - merchant_id responses: '200': description: Successful request. content: application/json: schema: type: object properties: message: type: string description: Success message. example: Success '400': description: Bad request. content: application/json: schema: $ref: '#/components/schemas/Error' examples: UserFieldRequired: summary: User object field required value: error_type: INVALID_REQUEST error_code: INVALID_FIELD error_message: The user.phone number is required. CardNumberNotNumeric: summary: Card number not numeric. value: error_type: INVALID_REQUEST error_code: INVALID_FIELD error_message: The card.number must be numeric. CardNumberTooLong: summary: Card number too long. value: error_type: INVALID_REQUEST error_code: INVALID_FIELD error_message: The card.number is too long for card type. CardNumberTooShort: summary: Card number too short. value: error_type: INVALID_REQUEST error_code: INVALID_FIELD error_message: The card.number is too short for card type. CardNumberInvalid: summary: Card number invalid. value: error_type: INVALID_REQUEST error_code: INVALID_FIELD error_message: >- The card.number is invalid and does not pass the Luhn check. CVVNotNumeric: summary: CVV not numeric value: error_type: INVALID_REQUEST error_code: INVALID_FIELD error_message: The card.cvv must be numeric. CVVTooLong: summary: CVV to long. value: error_type: INVALID_REQUEST error_code: INVALID_FIELD error_message: The card.cvv is too long for card type. CVVTooShort: summary: CVV to short. value: error_type: INVALID_REQUEST error_code: INVALID_FIELD error_message: The card.cvv is too short for card type. CardExpirationInvalid: summary: Card expiration invalid. value: error_type: INVALID_REQUEST error_code: INVALID_FIELD error_message: The card.expiration should be in MM/YYYY or MM/YY format. CardExpired: summary: Card expired. value: error_type: INVALID_REQUEST error_code: INVALID_FIELD error_message: The card is expired. OngoingOperation: summary: There is an existing operation value: error_type: MERCHANT_ACCOUNT_ERROR error_code: ONGOING_OPERATION error_message: An existing operation is in progress. '401': description: Unauthorized request. content: application/json: schema: $ref: '#/components/schemas/Error' examples: AuthFailed: summary: Auth failed value: error_type: INVALID_INPUT error_code: INVALID_API_KEYS error_message: Invalid client_id or secret provided. '403': description: Forbidden request. content: application/json: schema: $ref: '#/components/schemas/Error' examples: NoAccess: summary: No access value: error_type: INVALID_REQUEST error_code: NO_ACCESS error_message: Please contact Knot for access to this endpoint. components: schemas: Error: type: object properties: error_type: type: string description: Type of error. example: INVALID_REQUEST error_code: type: string description: Error code. example: INVALID_FIELD error_message: type: string description: Detailed error message. example: The user.name.first_name must not be greater than 255 characters. securitySchemes: basicAuth: type: http scheme: basic ````