> ## Documentation Index > Fetch the complete documentation index at: https://docs.impellabs.tech/llms.txt > Use this file to discover all available pages before exploring further. # Send a message > Sends a message into the conversation as the business owner. Answers 201. A person's reply takes the conversation over from the agent. On WhatsApp, a text outside the 24-hour window answers 422 with code `outside_customer_service_window`. Send a template then. Needs the `messages:write` scope. ## OpenAPI ````yaml /openapi/partner.yaml post /api/v1/partner/tenants/{external_ref}/conversations/{session_id}/messages/send/ openapi: 3.1.0 info: title: ImpelLabs Partner API version: '1' description: >- The Partner API provisions customer businesses (tenants) and runs their channels, conversations and templates from your own product. Call it from your server with a partner key. Every path ends with a slash. servers: - url: https://api.impellabs.tech security: - bearer: [] tags: - name: Keys description: Your partner API keys. - name: Tenants description: Customer businesses, their channels, conversations and templates. - name: Webhooks description: Where your tenants' events go. - name: WhatsApp sign-up description: The settings of the hosted WhatsApp sign-up. paths: /api/v1/partner/tenants/{external_ref}/conversations/{session_id}/messages/send/: post: tags: - Tenants summary: Send a message description: >- Sends a message into the conversation as the business owner. Answers 201. A person's reply takes the conversation over from the agent. On WhatsApp, a text outside the 24-hour window answers 422 with code `outside_customer_service_window`. Send a template then. Needs the `messages:write` scope. operationId: >- post_api_v1_partner_tenants_external_ref_conversations_session_id_messages_send parameters: - name: external_ref in: path required: true schema: type: string description: Your own id for the customer business, set when you created it. - name: session_id in: path required: true schema: type: string description: The conversation id (UUID). requestBody: content: application/json: schema: type: object properties: type: type: string description: >- One of `text`, `template`, `image`, `video`, `audio`, `document`, `interactive`, `location`, `reaction`. Default `text`. text: type: string description: The message text. Required for `text`. reply_to: type: string description: A message id or provider message id to quote. template_name: type: string description: The approved template to send. Required for `template`. lang: type: string description: The template language. Default `en_US`. body_params: type: array items: type: string description: The values for the template body. components: type: array items: type: object description: Template components, as Meta defines them. link: type: string description: A public link to the file, for a media type. media_id: type: string description: >- A provider media id, for a media type. Send `link` or `media_id`. caption: type: string description: A caption for a media type. 1024 characters at most. filename: type: string description: A file name for a document. payload: type: object description: For `interactive`, `location` and `reaction`. tag: type: string description: 'Messenger only: `HUMAN_AGENT`.' example: type: text text: Your visit is at 3 pm. required: false responses: '201': description: Success content: application/json: example: message: id: 9b3c1d5f-0000-4000-8000-000000000000 object: message role: user type: text text: Hello created_at: '2026-01-15T10:04:00+00:00' conversation: 5d2f7a3e-0000-4000-8000-000000000000 channel: name: whatsapp from: '+15550100101' conversation: id: 5d2f7a3e-0000-4000-8000-000000000000 object: conversation status: active agent: null agent_version: null channel: whatsapp external_ref: null turns: 3 metadata: {} created_at: '2026-01-15T10:00:00+00:00' updated_at: '2026-01-15T10:05:00+00:00' contact: name: Sam phone: '+15550100101' lead_id: 8a1e0c7b-0000-4000-8000-000000000000 human_control: 'on': false reason: '' since: '' state: ai pending_since: '' window: open: true last_inbound_at: '2026-01-15T10:04:00+00:00' closes_at: '2026-01-16T10:04:00+00:00' capabilities: can_text: true can_template: true can_media: true window_open: true window: open: true tags: [] whatsapp_number: '100000000000001' '400': $ref: '#/components/responses/Invalid' '401': $ref: '#/components/responses/Unauthorized' '403': $ref: '#/components/responses/Forbidden' '404': $ref: '#/components/responses/NotFound' 4XX: description: The request is not valid or not allowed content: application/json: schema: $ref: '#/components/schemas/Error' components: responses: Invalid: description: >- A field is missing or wrong. The body names each field: {"field": "what to fix"}. Unauthorized: description: The credentials are missing, wrong, expired or revoked. Forbidden: description: These credentials may not do this. NotFound: description: There is no such row, or these credentials cannot see it. schemas: Error: type: object description: >- An error. Most errors carry `detail`. Some carry `error` with `code` and `message`. properties: detail: type: string code: type: string field: type: string error: type: object properties: code: type: string message: type: string securitySchemes: bearer: type: http scheme: bearer ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.