> ## Documentation Index > Fetch the complete documentation index at: https://timelines.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # Send Message to Chat > Send a message into an existing WhatsApp chat or group specified by chat_id. ## OpenAPI ````yaml post /chats/{chat_id}/messages openapi: 3.0.3 info: title: Timelines Public API description: > # Timelines Public API _Some API calls may utilize message sending quota or be subject to message sending rate limits as described below._ ### Credit Utilization - Sending a message via API consumes 1 credit from message sending quota. - Sending a message with non-empty text and attachment consumes 2 credits from message sending quota. - If a message cannot be sent (invalid or not connected to WhatsApp number, WhatsApp server error), message sending quota will be restored (usually within a couple of hours). ### Message sending rate - Messages will be sent with random delay of about 2 seconds between each two messages (to avoid WhatsApp spam detection mechanisms). Contact support@timelines.ai if you want to modify delay for your workspace (available on Business plan only). - If you exceed message sending frequency, messages be queued and sent out with delay. Each queued message will consume a message sending credit, so the number of queued messages cannot exceed the available quota. ### Authorization: - Copy API token from [Public API page](https://app.timelines.ai/integrations/api/) in your TimelinesAI account. - Put the token in *Authorization* header of request as follows: ``` Authorization: Bearer 4d2d0239-e28c-4f4a-8a4d-3a3ca40056b8 ``` ### Message formatting: - use "\n" for line breaks version: 1.3.0 servers: - url: /integrations/api description: Public API root URL security: - bearerAuth: [] paths: /chats/{chat_id}/messages: post: summary: Send message in existing chat description: >- Send message into existing WhatsApp chat (or group) specified by chat_id. No need to specify WhatsApp Account, as each chat is already connected to a specific WhatsApp account in the TimelinesAI workspace. A message may contain a plaintext body or an attachment or both. parameters: - $ref: '#/components/parameters/chat_id' requestBody: description: A JSON describing recipient and message payload. required: true content: application/json: schema: $ref: '#/components/schemas/MessageWithReply' responses: '200': description: Message accepted for async sending content: application/json: schema: $ref: '#/components/schemas/MessageSendResponse' '400': $ref: '#/components/responses/BadRequestError' '401': $ref: '#/components/responses/UnauthorizedError' '403': $ref: '#/components/responses/AccessDenied' '404': $ref: '#/components/responses/NotFound' components: parameters: chat_id: in: path name: chat_id schema: type: integer required: true description: >- an id of the chat as appears in TimelinesAI (can be found in the URL of the chat page, or in the payload of outbound webhook). _Supports sending messages to a group._ schemas: MessageWithReply: allOf: - type: object properties: reply_to: type: string nullable: true description: > UID of the message this message replies to. Must reference a message in the same workspace and WhatsApp account. Null or empty string is ignored. - $ref: '#/components/schemas/Message' MessageSendResponse: type: object required: - status - data properties: status: type: string example: ok enum: - ok - error data: $ref: '#/components/schemas/MessageID' Message: type: object properties: text: type: string maxLength: 2000 description: plain text message example: hello, world! file_uid: type: string description: attachment UID example: afa9d4dd-978d-4a14-aa1b-bd65c272e645 label: $ref: '#/components/schemas/Label' chat_name: type: string maxLength: 256 description: an exact name of the chat (or group) as appears in TimelinesAI) example: MyChat attachment_template_id: type: integer description: >- a template ID of the attachment to be sent. The template must be created in the workspace before sending a message with it. example: 123456 MessageID: type: object required: - message_uid properties: message_uid: type: string ErrorResponse: required: - message - status type: object properties: message: type: string status: type: string example: error enum: - ok - error error_code: type: string description: >- Stable, machine-readable error code. Use this for branching in client integrations. example: validation_error enum: - missing_credentials - invalid_token - member_not_found - permission_denied - plan_feature_unavailable - quota_exceeded - rate_limit_exceeded - validation_error - not_supported - internal_error errors: type: array description: >- Per-field validation diagnostics. Present on `validation_error` responses; absent on auth/authorization/quota errors. items: $ref: '#/components/schemas/ValidationError' Label: type: string maxLength: 64 description: >- assign label to the chat, in which the message is sent (create new label, if not exists) example: customer ValidationError: type: object required: - fields - msg properties: fields: type: array items: type: string description: >- Path of the offending field, as a list of keys/indexes from the request root. example: - url msg: type: string description: Validator message for that field. example: must be a valid http(s) URL responses: BadRequestError: description: Invalid parameters content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' UnauthorizedError: description: Access token is missing or invalid AccessDenied: description: Access denied content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' NotFound: description: Specified entities not found content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' securitySchemes: bearerAuth: type: http scheme: bearer ````