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

# Updates the agent's system prompt and/or begin message via the API

> Updates the agent's system prompt and/or begin message via the API.



## OpenAPI

````yaml /api-reference/openapi.json post /api/v2/update-agent-prompt
openapi: 3.1.0
info:
  title: Lawtte API
  version: v2
  description: >-
    REST API behind the Lawtte dashboard: AI voice and chat calls, agent
    configuration, leads, campaigns, contacts, and automation workflows.
  contact:
    name: Lawtte support
    email: contact@lawtte.ai
    url: https://www.lawtte.ai
servers:
  - url: https://www.lawtte.ai
    description: Production
security:
  - bearerAuth: []
tags:
  - name: Voice & Chat
    description: Manage AI voice calls and chat sessions powered by Donna AI.
  - name: Agent Config
    description: Read and update AI agent prompts, voices, and configurations.
  - name: Appointments
    description: Check availability and book appointments via Cal.com integration.
  - name: Webhooks
    description: Receive real-time events after calls end.
  - name: Leads
    description: Create, manage, and analyze leads captured by your AI agents.
  - name: Campaigns
    description: Create and launch outbound call campaigns to lists of leads.
  - name: Contacts
    description: >-
      Import and sync contacts from CSV, OpenPhone, RingCentral, and practice
      management systems.
  - name: Workflows
    description: >-
      Build and manage automation workflows using a visual node-based flow
      editor.
  - name: Utilities
    description: Helper endpoints for AI-powered data extraction and widget testing.
paths:
  /api/v2/update-agent-prompt:
    post:
      tags:
        - Agent Config
      summary: Updates the agent's system prompt and/or begin message via the API
      description: Updates the agent's system prompt and/or begin message via the API.
      operationId: post-update-agent-prompt
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
                - agentId
              properties:
                agentId:
                  type: string
                  description: Agent ID.
                generalPrompt:
                  type: string
                  description: New system prompt for the agent.
                beginMessage:
                  type: string
                  description: New opening message the agent speaks.
      responses:
        '200':
          description: Success
          content:
            application/json:
              schema:
                type: object
              example:
                success: true
        '401':
          description: Missing or invalid credentials
components:
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      description: 'Lawtte API key or session token: `Authorization: Bearer <token>`.'

````

## Related topics

- [Fetches the full agent configuration including its LLM prompt and begin message](/api-reference/agent-config/fetches-the-full-agent-configuration-including-its-llm-prompt-and-begin-message.md)
- [How to build an AI receptionist and intake system](/guides/build-an-ai-receptionist.md)
- [API overview](/api-reference/introduction.md)
- [Updates the voice parameters (voice ID, speed, pitch) of an agent](/api-reference/agent-config/updates-the-voice-parameters-voice-id-speed-pitch-of-an-agent.md)
- [Sends a message in an active chat session and returns the agent's reply](/api-reference/voice-&-chat/sends-a-message-in-an-active-chat-session-and-returns-the-agents-reply.md)