> ## Documentation Index > Fetch the complete documentation index at: https://docs.hifi.com/llms.txt > Use this file to discover all available pages before exploring further. # Add an external wallet > Register an external (client-owned) wallet against a counter party. The `address` must be valid for the specified `chain`. Re-submitting with the same `referenceId` and matching details returns the existing wallet; conflicting details return a conflict error. ## OpenAPI ````yaml https://production.hifi.com/api/v3/openapi.json post /v3/users/{userId}/counter-parties/{counterPartyId}/external-wallets openapi: 3.0.0 info: title: Hifi API version: 3.0.0 description: API documentation for HIFI servers: - url: https://production.hifi.com description: Production server - url: https://sandbox.hifi.com description: Sandbox server security: - bearerAuth: [] tags: - name: Common description: Common endpoints - name: User description: User endpoints - name: Counter Party description: Counter party endpoints - name: Crypto Transfer description: Crypto transfer and batch transfer endpoints - name: Wallet description: Wallet and wallet offer endpoints - name: External Account description: External bank account endpoints (under a counter party) - name: External Wallet description: External wallet endpoints (under a counter party) - name: External Card description: External card endpoints (under a counter party) - name: Token Swap description: Token swap endpoints - name: Bridge description: Bridge endpoints - name: Virtual Account description: Virtual account endpoints - name: Compliance description: Compliance and compliance link endpoints - name: Webhook Endpoint description: Webhook endpoint endpoints - name: File description: File upload endpoints - name: Onramp description: Onramp (fiat to crypto) endpoints - name: Offramp description: Offramp (crypto to fiat) endpoints - name: Orchestration Address description: Orchestration (liquidation) address endpoints - name: KYC Link description: Hosted and custom KYC/KYB link endpoints - name: Transfer Approval description: Transfer approval endpoints - name: Corridor description: Supported fiat/crypto transfer corridor endpoints - name: Migration description: v2-to-v3 ID mapping endpoints paths: /v3/users/{userId}/counter-parties/{counterPartyId}/external-wallets: post: tags: - External Wallet summary: Add an external wallet description: > Register an external (client-owned) wallet against a counter party. The `address` must be valid for the specified `chain`. Re-submitting with the same `referenceId` and matching details returns the existing wallet; conflicting details return a conflict error. operationId: v3AddExternalWallet parameters: - $ref: '#/components/parameters/UserIdPathParameter' - $ref: '#/components/parameters/CounterPartyIdPathParameter' requestBody: $ref: '#/components/requestBodies/AddExternalWalletBody' responses: '200': $ref: '#/components/responses/AddExternalWalletResponse' '400': $ref: '#/components/responses/BadRequestResponse' '401': $ref: '#/components/responses/UnauthorizedResponse' '409': $ref: '#/components/responses/ConflictResponse' '500': $ref: '#/components/responses/InternalServerErrorResponse' components: parameters: UserIdPathParameter: name: userId in: path schema: type: string pattern: ^user_[A-Za-z0-9]+$ description: ID of the user. required: true CounterPartyIdPathParameter: name: counterPartyId in: path required: true schema: type: string description: Public ID of the counter party (prefixed with `cpty_`) example: cpty_7bV1aLcs3Kf9dQ2mNpXwZ requestBodies: AddExternalWalletBody: required: true description: >- External wallet details. The `address` must be valid for the specified `chain`. content: application/json: schema: $ref: '#/components/schemas/WalletAddExternalBody' examples: EVMWallet: summary: EVM external wallet (Polygon) value: address: '0x9876543210fedcba9876543210fedcba98765432' chain: POLYGON name: Treasury cold wallet referenceId: my-ref-001 SolanaWallet: summary: Solana external wallet value: address: 7EqQdEULxWcraVx3mXKFjc84LhCkMGZCkRuDpvcMwJeK chain: SOLANA name: Ops wallet referenceId: my-ref-002 responses: AddExternalWalletResponse: description: External wallet added successfully. content: application/json: schema: $ref: '#/components/schemas/WalletExternalObject' example: id: extw_4mNpXwZ7bV1aLcs3Kf9dQ userId: usr_3Kf9dQ2mNpXwZ7bV1aLcs counterPartyId: cpty_7bV1aLcs3Kf9dQ2mNpXwZ chain: POLYGON name: Treasury cold wallet address: '0x9876543210fedcba9876543210fedcba98765432' referenceId: my-ref-001 active: true createdAt: '2026-07-01T10:30:00.000Z' updatedAt: '2026-07-01T10:30:00.000Z' BadRequestResponse: description: Bad Request — the request was malformed or failed validation. content: application/json: schema: $ref: '#/components/schemas/ApiError' example: type: VALIDATION_ERROR message: One or more fields are invalid or missing. fields: - code: invalid_value message: Must be a valid email address field: email UnauthorizedResponse: description: Unauthorized content: application/json: schema: $ref: '#/components/schemas/Unauthorized' ConflictResponse: description: >- Conflict — the request collides with the current state of the resource (e.g. idempotency-key reuse with a different payload). content: application/json: schema: $ref: '#/components/schemas/ApiError' example: type: RESOURCE_CONFLICT message: Resource already exists or conflicts with current state InternalServerErrorResponse: description: Internal Server Error content: application/json: schema: $ref: '#/components/schemas/InternalServerError' schemas: WalletAddExternalBody: type: object description: | External wallet details. The `address` must be a valid address for the specified `chain`. required: - address - chain - name - referenceId properties: address: type: string description: On-chain address of the external wallet. example: '0x9876543210fedcba9876543210fedcba98765432' chain: type: string enum: - POLYGON - SOLANA - ETHEREUM - BASE - BSC - FLOW_EVM - CANTON - TRON example: POLYGON name: type: string description: Human-readable name for the external wallet. example: Treasury cold wallet referenceId: type: string description: Client-supplied idempotency/reference identifier. example: my-ref-001 WalletExternalObject: type: object description: An external (client-owned) wallet registered against a counter party. properties: id: type: string description: Public ID of the external wallet (prefixed with `extw_`). example: extw_4mNpXwZ7bV1aLcs3Kf9dQ userId: type: string description: >- Public ID of the user this external wallet belongs to (prefixed with `usr_`). example: usr_3Kf9dQ2mNpXwZ7bV1aLcs counterPartyId: type: string description: >- Public ID of the counter party this external wallet belongs to (prefixed with `cpty_`). example: cpty_7bV1aLcs3Kf9dQ2mNpXwZ chain: type: string enum: - POLYGON - SOLANA - ETHEREUM - BASE - BSC - FLOW_EVM - CANTON - TRON example: POLYGON name: type: string description: Human-readable name for the external wallet. example: Treasury cold wallet address: type: string description: On-chain address of the external wallet. example: '0x9876543210fedcba9876543210fedcba98765432' referenceId: type: string description: Client-supplied idempotency/reference identifier. example: my-ref-001 active: type: boolean description: Whether the external wallet is active. example: true createdAt: type: string format: date-time example: '2026-07-01T10:30:00.000Z' updatedAt: type: string format: date-time example: '2026-07-01T10:30:00.000Z' ApiError: type: object description: >- Standard v3 error shape, returned by validation failures and business-logic errors alike. properties: type: type: string description: >- Machine-readable error type, e.g. VALIDATION_ERROR, ACTION_NOT_ALLOWED, RESOURCE_CONFLICT. example: VALIDATION_ERROR message: type: string description: Human-readable error message. example: One or more fields are invalid or missing. fields: type: array description: >- Present on field-level validation errors. One entry per problem field. items: type: object properties: code: type: string description: Error code related to the field issue. message: type: string description: Error message for the specific issue. field: type: string description: The name of the field that has an issue. Unauthorized: type: object properties: type: type: string description: Unauthorized enum example: UNAUTHORIZED message: type: string description: Unauthorized message example: Authentication required InternalServerError: type: object properties: type: type: string example: INTERNAL_SERVER_ERROR description: Internal server error enum message: type: string example: An internal server error occurred description: Internal server error message securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: JWT ````