> ## Documentation Index > Fetch the complete documentation index at: https://docs.passage.coinlist.co/llms.txt > Use this file to discover all available pages before exploring further. # Connect a proven external wallet to an offer option > For options without a whitelisted-wallet requirement, submitting when a wallet is already connected updates the existing binding in place, keeping its id. Options with a whitelisted-wallet requirement accumulate wallets up to the requirement's max_wallets and then reject with `max_wallets_reached`. ## OpenAPI ````yaml /api-reference/openapi.json post /v1/offers/{offer_id}/addresses openapi: 3.0.0 info: title: Frontline API version: 0.1.0 servers: - url: https://api.coinlist.co variables: {} security: [] tags: - name: DocumentSubmissions - name: KYC - name: OAuth - name: Offers - name: Participations - name: Pii - name: Requirements - name: Swap - name: Token - name: Wallet - name: Wallet Ownership paths: /v1/offers/{offer_id}/addresses: post: tags: - Offers summary: Connect a proven external wallet to an offer option description: >- For options without a whitelisted-wallet requirement, submitting when a wallet is already connected updates the existing binding in place, keeping its id. Options with a whitelisted-wallet requirement accumulate wallets up to the requirement's max_wallets and then reject with `max_wallets_reached`. operationId: createOfferOptionAddress parameters: - description: The ID of the offer in: path name: offer_id required: true schema: type: string x-struct: null x-validate: null requestBody: content: application/json: schema: $ref: '#/components/schemas/CreateOfferOptionAddressRequest' application/x-www-form-urlencoded: schema: $ref: '#/components/schemas/CreateOfferOptionAddressRequest' description: Offer option address params required: true responses: '200': content: application/json: schema: $ref: '#/components/schemas/OfferOptionAddress' description: Successful response. default: content: application/json: schema: $ref: '#/components/schemas/Error' description: Error response. callbacks: {} security: - OAuth2: [] components: schemas: CreateOfferOptionAddressRequest: additionalProperties: false description: > Connects a proven external wallet to an offer option. Requires a previously generated, unconsumed wallet-ownership challenge for the same wallet and chain. The signature is verified and the single-use challenge consumed during ownership verification, before the bind. A rejected bind does not roll back the consume, so the user re-signs to retry. properties: chain: description: The blockchain network the wallet belongs to. enum: - ethereum_sepolia - base_sepolia - solana_devnet - ethereum_mainnet - base_mainnet - solana_mainnet example: ethereum_sepolia type: string x-struct: null x-validate: null offer_option_id: description: The ID of the offer option to connect the wallet to. type: string x-struct: null x-validate: null signature: description: The cryptographic signature of the challenge message. example: '0xdeadbeef' type: string x-struct: null x-validate: null wallet_address: description: >- The external wallet address. For EVM chains, must be a valid Ethereum address (normalized to lowercase). example: '0x742d35cc6634c0532925a3b844bc9e7595f0beb1' type: string x-struct: null x-validate: null required: - offer_option_id - wallet_address - chain - signature title: CreateOfferOptionAddressRequest type: object x-struct: Elixir.FrontlineAPIWeb.OpenApi.Schemas.CreateOfferOptionAddressRequest x-validate: null OfferOptionAddress: additionalProperties: false description: A user's proven external wallet connected to an offer option. properties: address: description: The connected external wallet address. type: string x-struct: null x-validate: null created_at: description: When the binding was created. example: '2025-01-01T00:00:00.000000Z' format: date-time type: string x-struct: null x-validate: null id: description: Unique identifier for the object. example: 05edea81-98a7-4582-aa7c-040d57cb1858 type: string x-struct: null x-validate: null offer_option_id: description: The ID of the offer option. example: 05edea81-98a7-4582-aa7c-040d57cb1858 type: string x-struct: null x-validate: null protocol: description: >- The protocol the binding is scoped to. An EVM address binds once per option regardless of which EVM chain proved ownership. enum: - ethereum - solana type: string x-struct: null x-validate: null required: - id - offer_option_id - address - protocol - created_at title: OfferOptionAddress type: object x-struct: Elixir.FrontlineAPIWeb.OpenApi.Schemas.OfferOptionAddress x-validate: null Error: additionalProperties: false properties: code: description: A human-readable message providing more details about the error. type: string x-struct: null x-validate: null errors: additionalProperties: items: type: string x-struct: null x-validate: null type: array x-struct: null x-validate: null type: object x-struct: null x-validate: null event_id: description: >- The unique identifier for the error event. This is useful for tracking and debugging. type: string x-struct: null x-validate: null message: description: >- For some errors that could be handled programmatically, a short string indicating the error code reported. type: string x-struct: null x-validate: null type: description: >- The type of error returned. One of `api_error`, `invalid_request_error` enum: - api_error - invalid_request_error type: string x-struct: null x-validate: null required: - type - message title: Error type: object x-struct: Elixir.FrontlineAPIWeb.OpenApi.Schemas.ApiError x-validate: null securitySchemes: OAuth2: description: OAuth 2.0 authorization and token endpoints flows: authorizationCode: authorizationUrl: /oauth/authorize refreshUrl: /oauth/token scopes: {} tokenUrl: /oauth/token clientCredentials: refreshUrl: /oauth/token scopes: {} tokenUrl: /oauth/token type: oauth2 ````