# Create child public key

Derive and register a child key from an account-level public key.
The server derives the child extended public key using BIP-32 derivation: no cryptography
needed on the client side.

If a standalone key with the same derived value already exists in the project, it is adopted
as a child of this account key.

Only applicable to account-level keys (depth-3).

Endpoint: POST /public-keys/{public_key_id}/children
Version: 2.0.0
Security: Auth

## Security:

  - `Auth` (unknown)
    apiKey in header X-Api-Key scopes: api:public_key:write

## Path parameters:

  - `public_key_id` (string, required)
    Unique identifier (UUID) of the public key.

## Header parameters:

  - `Idempotency-Key` (string, required)
    Case-sensitive opaque key for one mutation intent. Send exactly one header occurrence containing 1 to 128 visible ASCII bytes (0x21..0x7e). Commas are literal data; do not trim, lowercase or require UUID syntax. Reuse the same key for retries, with current authorization checked on every attempt. Repeated header occurrences are rejected.

## Request fields (application/json):

  - `change` (integer, required)
    BIP-44 change index for child key derivation.
`0` = external chain (receiving addresses), `1` = internal chain (change addresses).
    Enum: "0", "1"

  - `label` (string, required)
    User-friendly label for the public key.
    Example: Main Bitcoin Wallet

## Request examples:

  - `External chain (receiving addresses)` (unknown)

  - `Internal chain (change addresses)` (unknown)

## Response 200:

  - `200` (unknown)
    Created child public key.

## Response 200 fields (application/json):

  - `item` (object, required)
    HD public key used to derive child addresses.
    Example: {"id":"550e8400-e29b-41d4-a716-446655440000","value":"xpub6EFxzN6ZgMCZ1PxeRigmAhm2UBGzXtZNgznCEaWuEt9efBpJwAXFA4ZckBdR1pdMQ1pBgsey7ebjToZ5gYXveftB3zwoQ8NvEkimvyaz34i","label":"Main Bitcoin Wallet","de…

  - `item.id` (string, required)
    Unique identifier (UUID).
    Example: 550e8400-e29b-41d4-a716-446655440000

  - `item.value` (string, required)
    BIP32/SLIP-0132 extended public key in Base58Check format.

  - `item.label` (string, required)
    User-friendly label for the public key.
    Example: Main Bitcoin Wallet

  - `item.derivation_path` (string, required)
    HD derivation path in BIP-44 format. Supports both account-level (`m/purpose'/coin_type'/account'`)
and change-level (`m/purpose'/coin_type'/account'/change`) paths.
Account-level paths (depth-3) represent HD wallet accounts and cannot derive addresses directly:
use the children endpoint to create change-level child keys first.

  - `item.children` (array)
    Child keys derived from this account-level key. Present only for account-level keys (depth-3).
Each child represents an external (change=0) or internal (change=1) chain.

  - `item.created_at` (string, required)
    Timestamp when the resource was created.
    Example: 2024-01-15T10:30:00Z

  - `item.updated_at` (string, required)
    Timestamp when the resource was last updated.
    Example: 2024-01-15T10:30:00Z

## Response 201:

  - `201` (unknown)
    Created child public key.

## Response 201 fields (application/json):

  - `item` (object, required)
    HD public key used to derive child addresses.
    Example: {"id":"550e8400-e29b-41d4-a716-446655440000","value":"xpub6EFxzN6ZgMCZ1PxeRigmAhm2UBGzXtZNgznCEaWuEt9efBpJwAXFA4ZckBdR1pdMQ1pBgsey7ebjToZ5gYXveftB3zwoQ8NvEkimvyaz34i","label":"Main Bitcoin Wallet","de…

  - `item.id` (string, required)
    Unique identifier (UUID).
    Example: 550e8400-e29b-41d4-a716-446655440000

  - `item.value` (string, required)
    BIP32/SLIP-0132 extended public key in Base58Check format.

  - `item.label` (string, required)
    User-friendly label for the public key.
    Example: Main Bitcoin Wallet

  - `item.derivation_path` (string, required)
    HD derivation path in BIP-44 format. Supports both account-level (`m/purpose'/coin_type'/account'`)
and change-level (`m/purpose'/coin_type'/account'/change`) paths.
Account-level paths (depth-3) represent HD wallet accounts and cannot derive addresses directly:
use the children endpoint to create change-level child keys first.

  - `item.children` (array)
    Child keys derived from this account-level key. Present only for account-level keys (depth-3).
Each child represents an external (change=0) or internal (change=1) chain.

  - `item.created_at` (string, required)
    Timestamp when the resource was created.
    Example: 2024-01-15T10:30:00Z

  - `item.updated_at` (string, required)
    Timestamp when the resource was last updated.
    Example: 2024-01-15T10:30:00Z

## Response 400:

  - `400` (unknown)
    Bad request (e.g., missing or invalid fields). Invalid text may be reported as address.label_invalid, address.meta_invalid, public_key.label_invalid, invoice.comment_invalid, invoice.metadata_invalid.

## Response 400 fields (application/problem+json):

  - `type` (string, required)
    A URI that identifies the error type.
    Example: https://docs.vilna.io/apis/errors#internal-error

  - `title` (string, required)
    A short summary of the error type.
Use `detail` for information specific to this occurrence.
    Example: Bad Request

  - `status` (integer, required)
    The HTTP status code for this error.
Matches the status code of the HTTP response.
    Example: 400

  - `detail` (string)
    A human-readable explanation of what went wrong in this specific case.
May be localized.
    Example: The address is already assigned to another invoice

  - `instance` (string)
    A URI that identifies this specific error occurrence.
Include this value when contacting support.
    Example: /traces/0123456789abcdef0123456789abcdef

  - `code` (string, required)
    Stable machine-readable error code for programmatic error handling. Unlike the HTTP `status` or free-form `detail`, this code is guaranteed not to change between versions for a given error condition, so it is safe to branch on in client code. Defaults to `unspecified` when the server has not assigned a specific code.
    Example: blockchain.not_found

  - `fields` (array)
    List of invalid fields in the request.

  - `fields.name` (string, required)
    The name of the invalid field.
    Example: max_len

  - `fields.reason` (string, required)
    Why this field is invalid.
    Example: 32

## Response 401:

  - `401` (unknown)
    Missing or invalid authentication credentials.

## Response 401 fields (application/problem+json):

  - `type` (string, required)
    A URI that identifies the error type.
    Example: https://docs.vilna.io/apis/errors#internal-error

  - `title` (string, required)
    A short summary of the error type.
Use `detail` for information specific to this occurrence.
    Example: Bad Request

  - `status` (integer, required)
    The HTTP status code for this error.
Matches the status code of the HTTP response.
    Example: 400

  - `detail` (string)
    A human-readable explanation of what went wrong in this specific case.
May be localized.
    Example: The address is already assigned to another invoice

  - `instance` (string)
    A URI that identifies this specific error occurrence.
Include this value when contacting support.
    Example: /traces/0123456789abcdef0123456789abcdef

  - `code` (string, required)
    Stable machine-readable error code for programmatic error handling. Unlike the HTTP `status` or free-form `detail`, this code is guaranteed not to change between versions for a given error condition, so it is safe to branch on in client code. Defaults to `unspecified` when the server has not assigned a specific code.
    Example: blockchain.not_found

## Response 403:

  - `403` (unknown)
    Insufficient permissions.

## Response 403 fields (application/problem+json):

  - `type` (string, required)
    A URI that identifies the error type.
    Example: https://docs.vilna.io/apis/errors#internal-error

  - `title` (string, required)
    A short summary of the error type.
Use `detail` for information specific to this occurrence.
    Example: Bad Request

  - `status` (integer, required)
    The HTTP status code for this error.
Matches the status code of the HTTP response.
    Example: 400

  - `detail` (string)
    A human-readable explanation of what went wrong in this specific case.
May be localized.
    Example: The address is already assigned to another invoice

  - `instance` (string)
    A URI that identifies this specific error occurrence.
Include this value when contacting support.
    Example: /traces/0123456789abcdef0123456789abcdef

  - `code` (string, required)
    Stable machine-readable error code for programmatic error handling. Unlike the HTTP `status` or free-form `detail`, this code is guaranteed not to change between versions for a given error condition, so it is safe to branch on in client code. Defaults to `unspecified` when the server has not assigned a specific code.
    Example: blockchain.not_found

## Response 404:

  - `404` (unknown)
    Requested resource does not exist.

## Response 404 fields (application/problem+json):

  - `type` (string, required)
    A URI that identifies the error type.
    Example: https://docs.vilna.io/apis/errors#internal-error

  - `title` (string, required)
    A short summary of the error type.
Use `detail` for information specific to this occurrence.
    Example: Bad Request

  - `status` (integer, required)
    The HTTP status code for this error.
Matches the status code of the HTTP response.
    Example: 400

  - `detail` (string)
    A human-readable explanation of what went wrong in this specific case.
May be localized.
    Example: The address is already assigned to another invoice

  - `instance` (string)
    A URI that identifies this specific error occurrence.
Include this value when contacting support.
    Example: /traces/0123456789abcdef0123456789abcdef

  - `code` (string, required)
    Stable machine-readable error code for programmatic error handling. Unlike the HTTP `status` or free-form `detail`, this code is guaranteed not to change between versions for a given error condition, so it is safe to branch on in client code. Defaults to `unspecified` when the server has not assigned a specific code.
    Example: blockchain.not_found

## Response 409:

  - `409` (unknown)
    Request conflicts with the current resource state.

## Response 409 fields (application/problem+json):

  - `type` (string, required)
    A URI that identifies the error type.
    Example: https://docs.vilna.io/apis/errors#internal-error

  - `title` (string, required)
    A short summary of the error type.
Use `detail` for information specific to this occurrence.
    Example: Bad Request

  - `status` (integer, required)
    The HTTP status code for this error.
Matches the status code of the HTTP response.
    Example: 400

  - `detail` (string)
    A human-readable explanation of what went wrong in this specific case.
May be localized.
    Example: The address is already assigned to another invoice

  - `instance` (string)
    A URI that identifies this specific error occurrence.
Include this value when contacting support.
    Example: /traces/0123456789abcdef0123456789abcdef

  - `code` (string, required)
    Stable machine-readable error code for programmatic error handling. Unlike the HTTP `status` or free-form `detail`, this code is guaranteed not to change between versions for a given error condition, so it is safe to branch on in client code. Defaults to `unspecified` when the server has not assigned a specific code.
    Example: blockchain.not_found

## Response 422:

  - `422` (unknown)
    Request preconditions were not met.

## Response 422 fields (application/problem+json):

  - `type` (string, required)
    A URI that identifies the error type.
    Example: https://docs.vilna.io/apis/errors#internal-error

  - `title` (string, required)
    A short summary of the error type.
Use `detail` for information specific to this occurrence.
    Example: Bad Request

  - `status` (integer, required)
    The HTTP status code for this error.
Matches the status code of the HTTP response.
    Example: 400

  - `detail` (string)
    A human-readable explanation of what went wrong in this specific case.
May be localized.
    Example: The address is already assigned to another invoice

  - `instance` (string)
    A URI that identifies this specific error occurrence.
Include this value when contacting support.
    Example: /traces/0123456789abcdef0123456789abcdef

  - `code` (string, required)
    Stable machine-readable error code for programmatic error handling. Unlike the HTTP `status` or free-form `detail`, this code is guaranteed not to change between versions for a given error condition, so it is safe to branch on in client code. Defaults to `unspecified` when the server has not assigned a specific code.
    Example: blockchain.not_found

  - `fields` (array)
    List of fields that failed precondition validation.

  - `fields.name` (string, required)
    The name of the field that failed validation.
    Example: status

  - `fields.reason` (string, required)
    Why the precondition failed for this field.
    Example: Cannot transition from archived to active state

## Response 429:

  - `429` (unknown)
    Resource quota exceeded. The response includes the effective limit for this scope. The applicable code and limit depend on the operation; examples illustrate different limits.

## Response 429 fields (application/problem+json):

  - `type` (string, required)
    A URI that identifies the error type.
    Example: https://docs.vilna.io/apis/errors#internal-error

  - `title` (string, required)
    A short summary of the error type.
Use `detail` for information specific to this occurrence.
    Example: Bad Request

  - `status` (integer, required)
    The HTTP status code for this error.
Matches the status code of the HTTP response.
    Example: 400

  - `detail` (string)
    A human-readable explanation of what went wrong in this specific case.
May be localized.
    Example: The address is already assigned to another invoice

  - `instance` (string)
    A URI that identifies this specific error occurrence.
Include this value when contacting support.
    Example: /traces/0123456789abcdef0123456789abcdef

  - `code` (string, required)
    Stable machine-readable code identifying the exhausted resource quota. The code is always
supplied by the service; clients branch on it instead of the human-readable detail.
    Example: address.quota_exceeded

  - `max` (integer, required)
    Effective maximum for this resource in the caller's scope. Zero prohibits new admissions;
it does not disable resources already held. This is the configured limit, not current usage.
    Example: 100

## Response 503:

  - `503` (unknown)
    The operation is temporarily unavailable. Please try again later.

## Response 503 fields (application/problem+json):

  - `type` (string, required)
    A URI that identifies the error type.
    Example: https://docs.vilna.io/apis/errors#internal-error

  - `title` (string, required)
    A short summary of the error type.
Use `detail` for information specific to this occurrence.
    Example: Bad Request

  - `status` (integer, required)
    The HTTP status code for this error.
Matches the status code of the HTTP response.
    Example: 400

  - `detail` (string)
    A human-readable explanation of what went wrong in this specific case.
May be localized.
    Example: The address is already assigned to another invoice

  - `instance` (string)
    A URI that identifies this specific error occurrence.
Include this value when contacting support.
    Example: /traces/0123456789abcdef0123456789abcdef

  - `code` (string, required)
    Stable machine-readable error code for programmatic error handling. Unlike the HTTP `status` or free-form `detail`, this code is guaranteed not to change between versions for a given error condition, so it is safe to branch on in client code. Defaults to `unspecified` when the server has not assigned a specific code.
    Example: blockchain.not_found

## Response default:

  - `default` (unknown)
    Unexpected error.

## Response default fields (application/problem+json):

  - `type` (string, required)
    A URI that identifies the error type.
    Example: https://docs.vilna.io/apis/errors#internal-error

  - `title` (string, required)
    A short summary of the error type.
Use `detail` for information specific to this occurrence.
    Example: Bad Request

  - `status` (integer, required)
    The HTTP status code for this error.
Matches the status code of the HTTP response.
    Example: 400

  - `detail` (string)
    A human-readable explanation of what went wrong in this specific case.
May be localized.
    Example: The address is already assigned to another invoice

  - `instance` (string)
    A URI that identifies this specific error occurrence.
Include this value when contacting support.
    Example: /traces/0123456789abcdef0123456789abcdef

  - `code` (string, required)
    Stable machine-readable error code for programmatic error handling. Unlike the HTTP `status` or free-form `detail`, this code is guaranteed not to change between versions for a given error condition, so it is safe to branch on in client code. Defaults to `unspecified` when the server has not assigned a specific code.
    Example: blockchain.not_found

## Response 400 examples:

  - `The request body contains malformed JSON` (unknown)

## Response 401 examples:

  - `The API service refused authentication` (unknown)

## Response 403 examples:

  - `The API key lacks the required permission` (unknown)

## Response 404 examples:

  - `The address does not exist in this project` (unknown)

  - `The invoice does not exist in this project` (unknown)

## Response 409 examples:

  - `The address already has an active invoice` (unknown)

  - `The address cannot be deleted while in use` (unknown)

  - `A v1-created subscription rejects trigger, filter or noise changes` (unknown)

  - `The notification already has a manual attempt queued or in flight` (unknown)

  - `Retention has cleared the content, so there is nothing to resend` (unknown)

  - `The notification is a channel test` (unknown)

## Response 422 examples:

  - `A confirmed invoice cannot be cancelled` (unknown)

## Response 429 examples:

  - `The project has reached its address quota` (unknown)

  - `A zero effective limit prohibits new resources` (unknown)

## Response 503 examples:

  - `The operation cannot be completed at present` (unknown)