> ## Documentation Index > Fetch the complete documentation index at: https://docs.fuseai.com/llms.txt > Use this file to discover all available pages before exploring further. # Build a company list from a contact list's companies > Builds a new company list from the companies the contact list's rows belong to. Async: 202 returns the created list (in `processing` state) and `sourceContacts`, the number of contacts examined; poll `GET /business/lists/{listId}` on the new id until `completionStatus` is `complete`. A source list still being built answers 409 LIST_PROCESSING — retry once its own `completionStatus` leaves `processing`. Errors: - `404` `LIST_NOT_FOUND` — No source list with that id is visible to the token owner. - `409` `LIST_NAME_TAKEN` — A list already carries the requested name. - `409` `LIST_PROCESSING` — The source list is still being built; retry once its completionStatus leaves processing. - `422` `CONTACT_LIST_REQUIRED` — The source list is a company list; companies are derived from a contact list's rows. - `422` `LIST_EMPTY` — The source list has no contacts to derive companies from. - `422` `INVALID_REQUEST` — CRM rejected the request for a reason outside the mapped set. - `422` `VALIDATION_FAILED` — name missing/blank or over 255 characters, or an unknown body key. - `429` `RATE_LIMITED` — The lists rate bucket (120 requests/minute, 10,000/day per token owner) is exhausted. Requires one of the following token scopes: lists. ## OpenAPI ````yaml /openapi.json post /business/lists/{listId}/derive-company-list openapi: 3.1.0 info: title: Fuse Business API version: 1.0.0 description: >- External API for lists, campaigns, prospect search and contacts. Authenticate with your API token as HTTP Basic. All paths are under /api/v1. servers: - url: https://api.tryfuse.ai/api/v1 description: Production security: - basicAuth: [] tags: - name: Lists - name: Custom columns - name: Smart columns - name: Exports - name: Campaigns - name: Knowledge hubs - name: Analytics - name: Website intent - name: Account - name: Prospect search - name: Campaign steps - name: Scheduled sends - name: Campaign templates - name: Agents - name: Research - name: Company search - name: Saved searches - name: Folders - name: Contacts paths: /business/lists/{listId}/derive-company-list: post: tags: - Lists summary: Build a company list from a contact list's companies description: >- Builds a new company list from the companies the contact list's rows belong to. Async: 202 returns the created list (in `processing` state) and `sourceContacts`, the number of contacts examined; poll `GET /business/lists/{listId}` on the new id until `completionStatus` is `complete`. A source list still being built answers 409 LIST_PROCESSING — retry once its own `completionStatus` leaves `processing`. Errors: - `404` `LIST_NOT_FOUND` — No source list with that id is visible to the token owner. - `409` `LIST_NAME_TAKEN` — A list already carries the requested name. - `409` `LIST_PROCESSING` — The source list is still being built; retry once its completionStatus leaves processing. - `422` `CONTACT_LIST_REQUIRED` — The source list is a company list; companies are derived from a contact list's rows. - `422` `LIST_EMPTY` — The source list has no contacts to derive companies from. - `422` `INVALID_REQUEST` — CRM rejected the request for a reason outside the mapped set. - `422` `VALIDATION_FAILED` — name missing/blank or over 255 characters, or an unknown body key. - `429` `RATE_LIMITED` — The lists rate bucket (120 requests/minute, 10,000/day per token owner) is exhausted. Requires one of the following token scopes: lists. operationId: deriveCompanyList parameters: - name: listId in: path required: true description: 24-character hex id of the list (from GET /business/lists). schema: type: string description: 24-character hex id of the list (from GET /business/lists). requestBody: required: true content: application/json: schema: type: object properties: name: type: string minLength: 1 maxLength: 255 description: >- Name for the new company list (1-255 characters); a name already in use answers 409 LIST_NAME_TAKEN. required: - name responses: '202': description: Success headers: RateLimit-Limit: schema: type: integer description: Requests permitted in the current window. RateLimit-Remaining: schema: type: integer description: Requests remaining in the current window. RateLimit-Reset: schema: type: integer description: Seconds until the current window resets. content: application/json: schema: type: object required: - list - sourceContacts properties: list: type: object required: - id - name properties: id: type: string name: type: string sourceContacts: type: - integer - 'null' example: list: id: 68a1f20b9c41d20014b3e977 name: Q3 fintech companies sourceContacts: 412 '400': description: Error content: application/json: schema: $ref: '#/components/schemas/Error' '401': description: Error content: application/json: schema: $ref: '#/components/schemas/Error' '402': description: Error content: application/json: schema: $ref: '#/components/schemas/Error' '403': description: Error content: application/json: schema: $ref: '#/components/schemas/Error' '404': description: Error content: application/json: schema: $ref: '#/components/schemas/Error' '409': description: Error content: application/json: schema: $ref: '#/components/schemas/Error' '422': description: Error content: application/json: schema: $ref: '#/components/schemas/Error' '429': description: Error content: application/json: schema: $ref: '#/components/schemas/Error' '500': description: Error content: application/json: schema: $ref: '#/components/schemas/Error' security: - basicAuth: [] components: schemas: Error: type: object properties: error: type: object properties: code: type: string message: type: string param: type: - string - 'null' doc_url: type: - string - 'null' request_id: type: - string - 'null' required: - code - message required: - error securitySchemes: basicAuth: type: http scheme: basic description: >- Your API token (`af_…`) as the Basic-auth username, with an empty password. ````