Vertex AI RAG Engine with ADK

Vertex AI RAG Engine is a fully managed retrieval-augmented generation service on Google Cloud. Instead of building and maintaining your own vector database, chunking pipeline, and retrieval logic, you create a RAG corpus on Vertex AI, upload your documents, and the platform handles embedding, indexing, and retrieval automatically. Your ADK agent can then use VertexAIRagRetrieval as a built-in tool - it queries the RAG corpus, retrieves relevant document chunks, and grounds its answers in your actual company content. No infrastructure to manage, no embedding model to deploy, no vector DB to maintain.

The workflow has two phases. First, create and populate a RAG corpus by uploading your documents to a Google Cloud Storage bucket and importing them into a corpus. Vertex AI automatically chunks, embeds, and indexes everything. Second, add VertexAIRagRetrieval as a tool to your ADK agent with the corpus resource name. The agent calls this tool when it needs to look up information from your documents and uses the retrieved content to give grounded, cited answers. The entire RAG infrastructure runs on Vertex AI with enterprise-grade security, VPC controls, and automatic scaling.

The below example builds a company HR policy Q&A agent that answers employee questions by retrieving from a managed RAG corpus of HR policy documents - grounded answers with document citations, zero RAG infrastructure code.

Building the ADK agent with the RAG tool and querying company policies,

It gives the following output with grounded answers citing source documents,

Employee: How many days of earned leave do I get per year?
HR Bot:   According to the ShopMax Leave Policy 2025, you are entitled to
          18 days of Earned Leave per year, accruing at 1.5 days per month.
          You can carry forward up to 30 days to the next year, and unused
          EL is encashable when you exit the company.
          [Source: HR_Leave_Policy_2025.pdf, Section 2]

Employee: Can I work from home during my probation period?
HR Bot:   No. As per the Work From Home Policy 2025, WFH is not permitted
          during your probation period (first 6 months). You become eligible
          for up to 2 WFH days per week after completing probation, subject
          to manager approval.
          [Source: WFH_Policy_2025.pdf, Section 3.1]

Employee: What is the maternity leave policy for the second child?
HR Bot:   The maternity leave entitlement is 26 weeks of fully paid leave
          for the first two children. The same 26-week entitlement applies
          for your second child. From the third child onwards, the entitlement
          reduces to 12 weeks.
          [Source: HR_Leave_Policy_2025.pdf, Section 5.2]

# All answers retrieved from managed Vertex AI RAG corpus
# Document citations included automatically
# Zero vector DB or embedding infrastructure maintained by you

New documents are indexed and searchable within minutes of upload,

New policy document added to corpus - agent answers updated immediately

hr-policy-corpus: projects/my-project/locations/us-central1/ragCorpora/1234

# Vertex AI RAG Engine handles: chunking, embedding, indexing, retrieval
# You only manage: which documents go in the corpus
# Scales to thousands of documents with no performance degradation

Vertex AI RAG Engine vs self-managed ChromaDB: use RAG Engine when you need enterprise-grade managed infrastructure with no ops overhead, GCP IAM access control on your knowledge base, automatic scaling beyond what a single ChromaDB instance handles, and when you are already deploying your agent on Vertex AI Agent Engine. Use self-managed ChromaDB (Tutorial 303) for cost-sensitive applications, local development, or when you need full control over the chunking and embedding strategy. For a production enterprise deployment on GCP, RAG Engine and Agent Engine together give you a fully managed end-to-end agent stack with enterprise security and zero infrastructure management.