VertexAiSearchTool fails with PUBLIC_WEBSITE datastores - "tool vertex_ai_search is not available"

[Ivan2125]

Description

VertexAiSearchTool fails with datastores that have contentConfig: PUBLIC_WEBSITE (website crawling), but works correctly with contentConfig: CONTENT_REQUIRED (GCS/PDF files).

Environment

• google-adk version: 1.22.1
• Python version: 3.12
• OS: Windows 11
• Deployment: Both local (adk web) and Vertex AI Agent Engine

Steps to Reproduce

1. Create a datastore from website crawling (PUBLIC_WEBSITE type)
2. Create an agent with VertexAiSearchTool pointing to that datastore
3. Run the agent locally with adk web or deploy to Agent Engine
4. Query the agent

Code Example

from google.adk.agents import LlmAgent
from google.adk.tools import VertexAiSearchTool

# This datastore is PUBLIC_WEBSITE type (website crawling)
WEB_DATASTORE_ID = "projects/{PROJECT_ID}/locations/global/collections/default_collection/dataStores/{WEBSITE_DATASTORE_ID}"

agent = LlmAgent(
    name="web_search_agent",
    model="gemini-2.5-flash-lite",
    instruction="Search for information",
    tools=[VertexAiSearchTool(data_store_id=WEB_DATASTORE_ID, max_results=8)],
)

Expected Behavior

The agent should search the datastore and return results.

Actual Behavior

The agent returns:

I am sorry, I cannot fulfill this request. The tool `vertex_ai_search` is not available.

Datastore Configuration Comparison

Datastore	contentConfig	Status
Website crawling	PUBLIC_WEBSITE	❌ FAILS
GCS/PDF files	CONTENT_REQUIRED	✅ WORKS

API Response for Failing Datastore (PUBLIC_WEBSITE)

{
  "name": "projects/{PROJECT_ID}/locations/global/collections/default_collection/dataStores/{WEBSITE_DATASTORE_ID}",
  "displayName": "Website_Datastore",
  "industryVertical": "GENERIC",
  "solutionTypes": ["SOLUTION_TYPE_SEARCH"],
  "contentConfig": "PUBLIC_WEBSITE",
  "defaultSchemaId": "default_schema"
}

API Response for Working Datastore (CONTENT_REQUIRED)

{
  "name": "projects/{PROJECT_ID}/locations/global/collections/default_collection/dataStores/{PDF_DATASTORE_ID}",
  "displayName": "PDF_Datastore",
  "industryVertical": "GENERIC",
  "solutionTypes": ["SOLUTION_TYPE_SEARCH"],
  "contentConfig": "CONTENT_REQUIRED",
  "defaultSchemaId": "default_schema",
  "documentProcessingConfig": {
    "defaultParsingConfig": {
      "digitalParsingConfig": {}
    }
  }
}

Additional Context

• The service account has roles/discoveryengine.admin permissions
• The datastores exist and are accessible via the Discovery Engine API
• The issue occurs both locally (adk web) and when deployed to Agent Engine
• Multiple agents in a ParallelAgent configuration, each with their own VertexAiSearchTool instance pointing to different datastores
• Only datastores with CONTENT_REQUIRED work, all PUBLIC_WEBSITE datastores fail with the same error

Possible Cause

It seems like VertexAiSearchTool may have different handling requirements for PUBLIC_WEBSITE vs CONTENT_REQUIRED datastores, possibly related to the SearchResultMode configuration (CHUNKS vs DOCUMENTS).