ADK Tools Guide

Tools are capabilities that agents can invoke during their reasoning process.
ADK supports several types of tools:

1. Function Tools
   Define Python functions and pass them directly to an agent.
   The function signature and docstring become the tool schema.

2. Retrieval Tools
   - FilesRetrieval: Index and search local files using embeddings.
     Uses gemini-embedding-2-preview by default.
   - VertexAiRagRetrieval: Search Vertex AI RAG corpora.

3. Code Execution
   Agents can generate and execute code in a sandboxed environment.

4. Third-Party Tool Integration
   - LangchainTool: Wraps LangChain tools for use in ADK.
   - CrewaiTool: Wraps CrewAI tools for use in ADK.

5. MCP Tools
   Connect to Model Context Protocol servers for external tool access.

Tool Configuration:
Tools can be configured with authentication, rate limiting, and custom
schemas. The ToolContext provides access to session state, artifacts,
and other contextual information during tool execution.