docs: add Amazon Bedrock Knowledge Base integration page

docs/integrations/bedrock-knowledge-base.md

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+---
+catalog_title: Amazon Bedrock Knowledge Base
+catalog_description: RAG retrieval from Amazon Bedrock Managed Knowledge Bases for ADK agents
+catalog_icon: /integrations/assets/bedrock-knowledge-base.png
+catalog_tags: ["tools", "rag", "aws"]
+---
+
+# Amazon Bedrock Knowledge Base
+
+<div class="language-support-tag">
+  <span class="lst-supported">Supported in ADK</span><span class="lst-python">Python</span>
+</div>
+
+Connect your ADK agents to [Amazon Bedrock Managed Knowledge Bases](https://docs.aws.amazon.com/bedrock/latest/userguide/knowledge-base.html) for retrieval-augmented generation (RAG). Agents can search enterprise documents and get grounded answers without hallucinating.
+
+## Why Bedrock Knowledge Bases for ADK?
+
+Amazon Bedrock Managed Knowledge Bases provide fully managed RAG infrastructure — no vector store to provision, no embeddings to configure, automatic scaling. Combined with ADK agents, your agent can:
+
+- **Search enterprise documents** (PDFs, web pages, databases) in natural language
+- **Use agentic retrieval** for multi-hop reasoning across documents
+- **Get grounded answers** with source citations
+- **Scale automatically** without managing infrastructure
+
+## Use cases
+
+- **Enterprise Q&A agents**: Answer questions from internal documentation, policies, and knowledge bases
+- **Customer support agents**: Retrieve relevant help articles and product information
+- **Research assistants**: Search across large document collections with multi-hop reasoning
+- **Compliance agents**: Look up regulatory documents and provide cited answers
+
+## Prerequisites
+
+- AWS account with Amazon Bedrock access
+- A Bedrock Managed Knowledge Base created (via [AWS Console](https://console.aws.amazon.com/bedrock/home#/knowledge-bases) or Terraform)
+- AWS credentials configured (environment variables, IAM role, or AWS profile)
+- Python 3.10+
+
+## Installation
+
+```bash
+pip install google-adk-community boto3>=1.43.2
+```
+
+## Use with agent
+
+```python
+from google.adk.agents import Agent
+from google.adk_community.tools.bedrock_kb import bedrock_kb_retrieve
+
+# Create an agent with Bedrock KB retrieval
+agent = Agent(
+    model="gemini-2.0-flash",
+    tools=[bedrock_kb_retrieve],
+    instruction="You are a helpful assistant. Use bedrock_kb_retrieve to search the knowledge base when answering questions about company policies or documentation.",
+)
+```
+
+The agent will automatically call `bedrock_kb_retrieve` when it needs information from the knowledge base.
+
+### Configuration via environment variables
+
+```bash
+export KNOWLEDGE_BASE_ID="YOUR_KB_ID"
+export AWS_REGION="us-west-2"
+export USE_AGENTIC_RETRIEVAL="true"  # Multi-hop reasoning (default)
+```
+
+### Configuration via function arguments
+
+```python
+# Pass knowledge_base_id directly (overrides env var)
+result = bedrock_kb_retrieve(
+    query="What is our refund policy?",
+    knowledge_base_id="YOUR_KB_ID",
+    max_results=5,
+)
+```
+
+## Available tools
+
+Tool | Description
+---- | -----------
+`bedrock_kb_retrieve` | Searches a Bedrock Managed Knowledge Base and returns relevant passages with sources and scores. Supports agentic retrieval (multi-hop reasoning) with automatic fallback to standard search.
+
+### Tool parameters
+
+Parameter | Type | Description
+--------- | ---- | -----------
+`query` | `str` | The natural language question or search query (required)
+`knowledge_base_id` | `str` | Bedrock KB ID. Defaults to `KNOWLEDGE_BASE_ID` env var
+`max_results` | `int` | Maximum results to return. Defaults to 5
+
+## Retrieval modes
+
+### Agentic retrieval (default)
+
+Uses `AgenticRetrieveStream` — the model reasons over multiple retrieval passes, decomposes complex queries, and applies managed reranking for better results.
+
+```bash
+export USE_AGENTIC_RETRIEVAL="true"
+```
+
+### Standard retrieval
+
+Uses `Retrieve` with `managedSearchConfiguration` — single-pass semantic search.
+
+```bash
+export USE_AGENTIC_RETRIEVAL="false"
+```
+
+## IAM permissions
+
+Your AWS credentials need:
+
+```json
+{
+    "Effect": "Allow",
+    "Action": [
+        "bedrock:Retrieve",
+        "bedrock:AgenticRetrieveStream"
+    ],
+    "Resource": "arn:aws:bedrock:REGION:ACCOUNT:knowledge-base/KB_ID"
+}
+```
+
+## Resources
+
+- [Amazon Bedrock Knowledge Bases documentation](https://docs.aws.amazon.com/bedrock/latest/userguide/knowledge-base.html)
+- [Create a managed knowledge base](https://docs.aws.amazon.com/bedrock/latest/userguide/kb-managed-create.html)
+- [AgenticRetrieveStream API](https://docs.aws.amazon.com/bedrock/latest/APIReference/API_agent-runtime_AgenticRetrieveStream.html)
+- [GitHub: adk-python-community](https://github.com/google/adk-python-community)