> ## Documentation Index > Fetch the complete documentation index at: https://docs.qfex.com/llms.txt > Use this file to discover all available pages before exploring further. # Create Builder Code > Create the authenticated user's builder code. The code is generated server-side as a UUID and stored with active=true. Specify both QFEX and builder fee shares in basis points; they need not sum to 10000. QFEX share must be at least 5000 (50%), builder share must be >= 0, and their sum must be at most 10000. After create, reload builder-code mappings on clearing house. ## OpenAPI ````yaml https://api.qfex.com/contracts/2026-10-29/openapi.yaml post /user/builder-code openapi: 3.1.0 info: contact: email: support@qfex.com name: QFEX Support description: REST API for QFEX license: name: QFEX License url: https://qfex.com/license title: QFEX REST API version: '2026-10-29' servers: - description: Production server url: https://api.qfex.com security: [] paths: /user/builder-code: post: tags: - user - builder summary: Create Builder Code description: >- Create the authenticated user's builder code. The code is generated server-side as a UUID and stored with active=true. Specify both QFEX and builder fee shares in basis points; they need not sum to 10000. QFEX share must be at least 5000 (50%), builder share must be >= 0, and their sum must be at most 10000. After create, reload builder-code mappings on clearing house. operationId: create-builder-code parameters: - description: >- Published API contract date. Omit or use latest for the latest contract; explicit dates stay pinned. Applies to request validation and response format. in: query name: api_version schema: examples: - '2026-10-29' type: string requestBody: content: application/json: schema: $ref: '#/components/schemas/CreateBuilderCodeRequestBody' required: true responses: '200': content: application/json: schema: $ref: '#/components/schemas/BuilderCodeDetails' description: OK default: content: application/problem+json: schema: $ref: '#/components/schemas/ErrorModel' description: Error security: - HMACSignature: [] Nonce: [] PublicKey: [] Timestamp: [] components: schemas: CreateBuilderCodeRequestBody: additionalProperties: false properties: $schema: description: A URL to the JSON Schema for this object. examples: - >- https://api.qfex.com/contracts/2026-10-29/schemas/CreateBuilderCodeRequestBody.json format: uri readOnly: true type: string builder_fee_share_bps: examples: - 3000 format: int64 maximum: 5000 minimum: 0 type: integer qfex_fee_share_bps: examples: - 5000 format: int64 maximum: 10000 minimum: 5000 type: integer required: - qfex_fee_share_bps - builder_fee_share_bps type: object BuilderCodeDetails: additionalProperties: false properties: $schema: description: A URL to the JSON Schema for this object. examples: - >- https://api.qfex.com/contracts/2026-10-29/schemas/BuilderCodeDetails.json format: uri readOnly: true type: string builder_code: type: string builder_fee_share_bps: format: int64 type: integer builder_fee_share_percent: format: double type: number created_at: format: date-time type: string qfex_fee_share_bps: format: int64 type: integer qfex_fee_share_percent: format: double type: number updated_at: format: date-time type: string required: - builder_code - qfex_fee_share_bps - qfex_fee_share_percent - builder_fee_share_bps - builder_fee_share_percent - created_at - updated_at type: object ErrorModel: additionalProperties: false properties: $schema: description: A URL to the JSON Schema for this object. examples: - https://api.qfex.com/contracts/2026-10-29/schemas/ErrorModel.json format: uri readOnly: true type: string detail: description: >- A human-readable explanation specific to this occurrence of the problem. examples: - Property foo is required but is missing. type: string errors: description: Optional list of individual error details items: $ref: '#/components/schemas/ErrorDetail' type: - array - 'null' instance: description: >- A URI reference that identifies the specific occurrence of the problem. examples: - https://example.com/error-log/abc123 format: uri type: string status: description: HTTP status code examples: - 400 format: int64 type: integer title: description: >- A short, human-readable summary of the problem type. This value should not change between occurrences of the error. examples: - Bad Request type: string type: default: about:blank description: A URI reference to human-readable documentation for the error. examples: - https://example.com/errors/example format: uri type: string type: object ErrorDetail: additionalProperties: false properties: location: description: >- Where the error occurred, e.g. 'body.items[3].tags' or 'path.thing-id' type: string message: description: Error message text type: string value: description: The value at the given location type: object securitySchemes: HMACSignature: description: HMAC-SHA256 signature (hex-encoded). in: header name: x-qfex-hmac-signature type: apiKey x-stoplight: hideExamples: true Nonce: description: Unique request nonce (hex encoded, max 100 characters). in: header name: x-qfex-nonce type: apiKey x-stoplight: hideExamples: true PublicKey: description: >- QFEX API Authentication requires these headers: - **x-qfex-public-key**: Your public API key - **x-qfex-hmac-signature**: HMAC signature of the request (hex encoded) - **x-qfex-nonce**: Unique nonce for the request (hex encoded, max 100 characters) - **x-qfex-timestamp**: Unix timestamp of the request These four are required. Optionally send **x-qfex-requested-account-id** (UUID) to act as a subaccount; see Signature Generation below. **Signature Generation:** 1. Generate a cryptographically secure random nonce (hex encoded, max 100 characters) and capture the current Unix timestamp. 2. Build the string `${nonce}:${unix_ts}` and compute an HMAC-SHA256 using your secret key. 3. Hex-encode the HMAC result to get the signature. 4. Send the required auth headers below. The nonce must be unique within a 15 minute window. **Important:** The signature itself must be hex-encoded before being sent in the `x-qfex-hmac-signature` header. **Optional header:** `x-qfex-requested-account-id` (UUID) selects an account where the authenticated user is a member; omit it to use the primary account. in: header name: x-qfex-public-key type: apiKey x-stoplight: hideExamples: true Timestamp: description: Unix timestamp (seconds since epoch). in: header name: x-qfex-timestamp type: apiKey x-stoplight: hideExamples: true ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.