Vertex AI Agent Builder Complete Guide: Conversational Agents, Vertex AI Search & Tool Use

Vertex AI Agent Builder is GCP's Gen AI agent-building platform, bundling Conversational Agents (the Dialogflow CX successor), Vertex AI Search, Tool Use, and Grounding into a single offering. It lets you build production-grade AI agents with no-code or low-code, and it has been Google's strategic agent service since 2024.

Core Components

• Conversational Agents: conversational agents (Dialogflow CX successor)
• Vertex AI Search: unified search plus answer generation
• Generative Playbook: flow definition in natural language
• Tool Use: OpenAPI / Cloud Functions integration
• Grounding: Vertex Search + Google Search + webhooks
• Conversation Profile: tone and style configuration

The Three Agent Types

Vertex AI Search Variants

Playbook Example (Markdown-style)

# Goal
Help the user check the status of their delivery

# Instructions
1. Confirm the order number
2. Call ${TOOL: get_order_status} to retrieve the status
3. If the order is in transit, return the carrier and tracking URL
4. If the order is delayed, route the user to ${TOOL: contact_support}

# Examples
User: I want to check on my order
Agent: Could you share your order number?

User: ORD-12345
Agent: Looking it up... ORD-12345 is in transit with Yamato Transport, tracking number ...

Tool Registration Example (OpenAPI)

openapi: 3.0.0
info:
  title: Order API
  version: 1.0.0
paths:
  /orders/{order_id}/status:
    get:
      operationId: get_order_status
      parameters:
        - name: order_id
          in: path
          required: true
          schema: {type: string}
      responses:
        '200':
          description: Order status
          content:
            application/json:
              schema:
                properties:
                  status: {type: string}
                  tracking_url: {type: string}

A Typical Architecture

1. Customer channels (Web / LINE / WhatsApp) → Agent Builder
2. The Agent classifies user intent according to the Playbook
3. Tools invoke internal APIs
4. Vertex AI Search searches internal documents
5. Gemini generates the response with citations
6. Audit Log stores every conversation in BigQuery for improvement analytics

Pricing

Comparison with Other Platforms

* Google Cloud and Vertex AI are trademarks of Google LLC. For the latest details, see the official Agent Builder page.