> ## Documentation Index > Fetch the complete documentation index at: https://chatbase.co/docs/llms.txt > Use this file to discover all available pages before exploring further. # Add a message to a ticket > Posts an agent reply to a ticket on behalf of a team member. Delivery to the customer is asynchronous; a 201 confirms the reply was recorded, not delivered. Posting a reply may transition the ticket status, matching dashboard behavior. ## OpenAPI ````yaml /api-v2-merged-openapi.json post /agents/{agentId}/helpdesk/tickets/{ticketNumber}/messages openapi: 3.1.0 info: title: Chatbase API v2 version: 2.0.0 description: >- Chatbase API v2 - A robust, structured API for managing agents, conversations, and the helpdesk. servers: - url: https://www.chatbase.co/api/v2 description: Chatbase API v2 security: [] paths: /agents/{agentId}/helpdesk/tickets/{ticketNumber}/messages: post: tags: - Helpdesk summary: Add a message to a ticket description: >- Posts an agent reply to a ticket on behalf of a team member. Delivery to the customer is asynchronous; a 201 confirms the reply was recorded, not delivered. Posting a reply may transition the ticket status, matching dashboard behavior. parameters: - schema: type: string minLength: 1 description: The agent ID example: 5QHA6VB-DIAbBhxwqxfdi required: true description: The agent ID name: agentId in: path - schema: type: integer exclusiveMinimum: 0 maximum: 2147483647 description: The ticket number example: 123 required: true description: The ticket number name: ticketNumber in: path requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/CreateTicketMessageBody' responses: '201': description: The created message content: application/json: schema: $ref: '#/components/schemas/CreatedTicketMessage' '400': description: >- The request body failed schema validation. Inspect the `details` object in the error response for field-level errors. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: VALIDATION_INVALID_BODY message: Invalid request '401': description: >- No Authorization header present. Provide a valid API key as a Bearer token in the Authorization header: `Authorization: Bearer `. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: AUTH_MISSING_API_KEY message: Authentication required '403': description: >- Your current plan does not include API access. Upgrade to the Standard plan or higher to use the API. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: SUBSCRIPTION_API_RESTRICTED_PLAN message: A Standard plan or higher is required to access the API '404': description: >- No ticket matches the provided ticket number for this agent. Verify the ticket number in the request path. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: TICKET_NOT_FOUND message: The requested ticket could not be found '409': description: >- This ticket is linked to a live conversation that has not been taken over from the AI agent, so a human reply cannot be posted. Take over the conversation from the dashboard first. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: CONVERSATION_NOT_TAKEN_OVER message: The linked conversation is not taken over '422': description: >- The authorId or authorEmail does not resolve to a member of your account. Authors must be existing team members. Also returned with code `MESSAGE_CONTENT_NOT_RENDERABLE` when the message body renders to empty HTML. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: TEAM_MEMBER_NOT_FOUND message: No team member matches the provided author '429': description: >- Rate limit exceeded. Check the `X-RateLimit-Reset` response header for the Unix epoch seconds when the limit resets. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: RATE_LIMIT_TOO_MANY_REQUESTS message: Too many requests, please try again later '500': description: >- An unhandled server error occurred. If the issue persists, contact support with the `x-request-id` response header value for debugging. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: INTERNAL_SERVER_ERROR message: Something went wrong, please try again '503': description: >- Chatbase is undergoing scheduled maintenance and the API is temporarily rejecting requests. This is transient; retry after a short delay. Requests are rejected before any data is read or written, so no partial changes are applied. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: SERVICE_UNDER_MAINTENANCE message: >- The API is temporarily unavailable for scheduled maintenance, please try again later security: - bearerAuth: [] components: schemas: CreateTicketMessageBody: type: object properties: type: type: string enum: - reply description: >- Message type. Only `reply` (customer-visible, delivered to the customer) is supported. example: reply content: type: string minLength: 1 maxLength: 10000 description: >- Message body as GitHub-flavored Markdown. Plain text is valid markdown; single newlines are kept as line breaks. Raw inline HTML is stripped. Limited to 10,000 characters after trimming. example: Thanks for reaching out. This is **fixed** now. authorId: type: string format: uuid description: >- Platform user id of the team member the reply is attributed to. Provide exactly one of authorId / authorEmail. authorEmail: type: string format: email description: >- Email of the team member the reply is attributed to (case-insensitive). Provide exactly one of authorId / authorEmail. example: sam@example.com required: - type - content CreatedTicketMessage: type: object properties: id: type: string description: Message id type: type: string enum: - reply description: Message type example: reply sender: allOf: - $ref: '#/components/schemas/MessageSender' - description: The team member the reply is attributed to content: type: string description: Rendered, sanitized HTML body contentText: type: string description: The raw markdown body as submitted createdAt: type: string description: ISO 8601 creation timestamp example: '2026-07-29T09:00:00.000Z' required: - id - type - sender - content - contentText - createdAt ErrorResponse: type: object properties: error: type: object properties: code: type: string description: Machine-readable error code message: type: string description: Human-readable error message details: type: object additionalProperties: type: string description: Field-level validation errors required: - code - message required: - error MessageSender: type: - object - 'null' properties: type: type: string enum: - customer - agent - system description: Who sent the message example: customer id: type: - string - 'null' description: 'Sender id: a platform user id for agents, a contact id for customers' name: type: - string - 'null' description: Sender name email: type: - string - 'null' description: Sender email required: - type - id - name - email description: Null on `event` messages securitySchemes: bearerAuth: type: http scheme: bearer description: API key from your account settings ````