> ## Documentation Index
> Fetch the complete documentation index at: https://docs.open.cx/llms.txt
> Use this file to discover all available pages before exploring further.

> Add an existing company to a contact. Adds rather than replaces, so a contact can belong to several companies.

# Add a company to a contact



## OpenAPI

````yaml post /contacts/{contact_id}/companies
openapi: 3.1.0
info:
  title: OpenCX API
  description: >

    OpenCX is an AI-powered, all-in-one platform for customer support and
    outbound communications.


    Use this API to manage your OpenCX organization's AI agents, actions,
    conversations, contacts, and more.


    To get started, generate a new API key from the dashboard.


    ## Authentication

    All API endpoints require authentication using a Bearer token. You can
    generate an API key from your OpenCX dashboard.


    ## Rate Limiting

    API requests are rate limited to ensure fair usage. The current limits are:

    - 100 requests per minute for standard endpoints

    - 1000 requests per minute for streaming endpoints


    ## Error Handling

    The API uses standard HTTP status codes and returns detailed error messages
    in the response body.
  version: 1.0-beta
  license:
    name: MIT
    url: https://opensource.org/licenses/MIT
servers:
  - url: http://localhost:8080
    description: Development
  - url: https://api.open.cx
    description: Production
security:
  - bearerAuth: []
paths:
  /contacts/{contact_id}/companies:
    post:
      summary: Add a company to a contact
      description: >-
        Links the contact to an EXISTING company, resolved by the organization's
        own key (`external_id`). Unknown keys are rejected rather than creating
        a company. A contact may belong to several companies, so this adds
        rather than replaces; linking the same company twice reports
        `unchanged`.
      operationId: linkContactToCompany
      parameters:
        - schema:
            type: string
            format: uuid
            pattern: >-
              ^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}|00000000-0000-0000-0000-000000000000|ffffffff-ffff-ffff-ffff-ffffffffffff)$
          in: path
          name: contact_id
          required: true
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/LinkContactCompanyDto'
      responses:
        '201':
          description: Default Response
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/LinkContactCompanyOutput'
        '500':
          description: Internal Server Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorDto'
components:
  schemas:
    LinkContactCompanyDto:
      $schema: https://json-schema.org/draft/2020-12/schema
      $id: '#/components/schemas/LinkContactCompanyDtoInput'
      type: object
      properties:
        external_id:
          type: string
          minLength: 1
      required:
        - external_id
    LinkContactCompanyOutput:
      $schema: https://json-schema.org/draft/2020-12/schema
      $id: '#/components/schemas/LinkContactCompanyOutput'
      type: object
      properties:
        outcome:
          type: string
          enum:
            - linked
            - unchanged
          description: '`unchanged` means the contact was already in this company.'
        company:
          $ref: '#/components/schemas/Company'
      required:
        - outcome
        - company
      additionalProperties: false
    ErrorDto:
      type: object
      properties:
        statusCode:
          type: integer
        message:
          type: string
        error:
          type: string
    Company:
      $schema: https://json-schema.org/draft/2020-12/schema
      $id: '#/components/schemas/Company'
      type: object
      properties:
        id:
          type: string
          format: uuid
          pattern: >-
            ^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}|00000000-0000-0000-0000-000000000000|ffffffff-ffff-ffff-ffff-ffffffffffff)$
        external_id:
          type: string
          description: The organization's own key for this company
        name:
          type: string
        custom_data:
          anyOf:
            - type: object
              propertyNames:
                type: string
              additionalProperties:
                anyOf:
                  - type: string
                  - type: number
                  - type: boolean
            - type: 'null'
        created_at:
          type: string
          description: ISO 8601 timestamp of when the company was created
        updated_at:
          type: string
          description: ISO 8601 timestamp of when the company was last updated
      required:
        - id
        - external_id
        - name
        - custom_data
        - created_at
        - updated_at
      additionalProperties: false
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT

````