[zyantw]

Staged: https://deploy-preview-2081--adk-docs-preview.netlify.app/tools-custom/mcp-tools/

PR Summary & Consolidation Mapping

This PR refactors and expands the Model Context Protocol (MCP) documentation in ADK. Previously, all MCP documentation was consolidated into a single monolithic 1,300-line page (docs/tools-custom/mcp-tools.md), mixing introductory tutorials, multi-language snippets, deployment guides, and advanced runtime configurations.

This PR modularizes the content into a streamlined 5-page documentation suite organized by developer use case, adds comprehensive multi-language support (Python, TypeScript, Go, Java, and Kotlin), and incorporates technical patterns validated against all five language SDK repositories.

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Comparison: Original Page (main) vs. PR Changes (HEAD)

Dimension	Original Page (main: mcp-tools.md)	PR Changes (HEAD: 5 Modular Pages)
Structure & Length	Single monolithic file (~1,300 lines) covering basics, deployment, server creation, and troubleshooting in one place.	Modular 5-page guide (~1,450 lines total), cleanly separated by developer journey and architecture.
Core Guide (mcp-tools.md)	Mixed introductory setup with container configuration, GKE manifests, and troubleshooting scripts.	Streamlined into a quickstart focused on client concepts, architecture sequence diagrams, and local/remote quickstarts across 5 languages.
Advanced Production Features	Limited mention of basic progress callbacks and headers.	New Page (mcp-tools-advanced.md): Dedicated guide for dynamic per-user header_provider, require_confirmation human-in-the-loop approvals, session-aware progress factories, standalone Runner lifecycle teardown, tool_name_prefix namespacing, bi-directional sampling/elicitation, and interactive UI widget rendering.
Serving ADK over MCP	Basic custom script example buried in the middle of the client tutorial.	New Page (agent-as-mcp-server.md): Complete guide covering one-line agent publishing via to_mcp_server(agent), low-level tool conversion via adk_to_mcp_tool_type, stdio server lifecycle, and client testing.
Hierarchical Multi-Agent Delegation	Not covered.	New Page (agent-managed-mcp.md): Architectural guide on encapsulating MCP toolsets inside sub-agents using AgentTool, applying cognitive tool_filter, eliminating parent context window bloat, and enabling model tiering.
Production Deployment	Scattered sections on Dockerfiles and raw GKE YAML snippets.	New Page (mcp-deployment.md): Dedicated deployment reference emphasizing synchronous agent definition rules, Cloud Run Streamable HTTP ASGI microservices, GKE sidecars, and Agent Runtime commands.
Multi-Language Parity	Partial Python and Java snippets; missing Kotlin.	Complete, verified code samples across Python, TypeScript, Go, Java, and Kotlin.

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Key Technical Claims & Repository Verification

1. Go SDK Transport & Tool Filtering

• Doc File: docs/tools-custom/mcp-tools.md
• Claim: In ADK Go, MCP integration uses github.com/modelcontextprotocol/go-sdk/mcp with mcptoolset.New accepting mcp.CommandTransport and tool.AllowedToolsPredicate.
• Repository Proof:
  • Dependency Declaration: google/adk-go/go.mod:18

    require (
    	github.com/google/go-cmp v0.7.0
    	github.com/modelcontextprotocol/go-sdk v1.1.0
    	google.golang.org/genai v0.9.0
    )

  • Constructor Signature: google/adk-go/tool/mcptoolset/set.go:44-58

    func New(cfg Config) (tool.Toolset, error) {
    	transport, err := buildTransport(cfg)
    	if err != nil {
    		return nil, err
    	}
    	return &set{
    		mcpClient:                   newConnectionRefresher(cfg.Client, transport),
    		toolFilter:                  cfg.ToolFilter,
    		requireConfirmation:         cfg.RequireConfirmation,
    		requireConfirmationProvider: cfg.RequireConfirmationProvider,
    	}, nil
    }

---

2. TypeScript Remote Connection Headers Configuration

• Doc File: docs/tools-custom/mcp-tools.md
• Claim: In ADK TypeScript (@google/adk), custom headers for remote StreamableHTTPConnectionParams must be passed via transportOptions.requestInit.headers.
• Repository Proof:
  • Interface Definition: google/adk-js/core/src/tools/mcp/mcp_session_manager.ts:53-66

    export interface StreamableHTTPConnectionParams {
      type: 'StreamableHTTPConnectionParams';
      url: string;
      /**
       * @deprecated
       * Use transportOptions.requestInit.headers instead.
       */
      header?: Record<string, unknown>;
      timeout?: number;
      sseReadTimeout?: number;
      terminateOnClose?: boolean;
      transportOptions?: StreamableHTTPClientTransportOptions;
    }

---

3. Sub-Agent Wrapping & Description Delegation (AgentTool)

• Doc File: docs/tools-custom/agent-managed-mcp.md
• Claim: In ADK Python, AgentTool wraps an LlmAgent as a callable tool, automatically deriving its name and description from the child agent without accepting a direct description keyword argument.
• Repository Proof:
  • Constructor Definition: google/adk-python/src/google/adk/tools/agent_tool.py:137-152

      def __init__(
          self,
          agent: BaseAgent,
          skip_summarization: bool = False,
          *,
          include_plugins: bool = True,
          propagate_grounding_metadata: bool = False,
      ):
        self.agent = agent
        self.skip_summarization: bool = skip_summarization
        self.include_plugins = include_plugins
        self.propagate_grounding_metadata = propagate_grounding_metadata
    
        super().__init__(name=agent.name, description=agent.description)

---

4. Human-In-The-Loop Confirmation Argument Introspection

• Doc File: docs/tools-custom/mcp-tools-advanced.md
• Claim: ADK Python dynamically introspects require_confirmation callable parameters against incoming tool arguments, requiring parameter names (such as query) or **kwargs.
• Repository Proof:
  • Argument Preparation Logic: google/adk-python/src/google/adk/tools/mcp_tool/mcp_tool.py:427-440

      def _prepare_callable_args(
          self,
          target: Callable[..., Any],
          args: dict[str, Any],
          tool_context: ToolContext,
      ) -> dict[str, Any]:
        """Prepares arguments for invoking a user-provided callable."""
        args_to_call = args.copy()
        try:
          signature = inspect.signature(target)
        except (ValueError, TypeError):
          return args_to_call
    
        valid_params = set(signature.parameters.keys())
        has_kwargs = any(
            param.kind == inspect.Parameter.VAR_KEYWORD
            for param in signature.parameters.values()
        )

---

5. One-Line Agent Conversion to MCP Server (to_mcp_server)

• Doc File: docs/tools-custom/agent-as-mcp-server.md
• Claim: ADK Python provides to_mcp_server(agent) to publish an entire LlmAgent as a standard FastMCP server over stdio.
• Repository Proof:
  • Function Declaration: google/adk-python/src/google/adk/tools/mcp_tool/_agent_to_mcp.py:34-45

    def to_mcp_server(
        agent: BaseAgent,
        runner: Runner | None = None,
        name: str | None = None,
        **fastmcp_kwargs: Any,
    ) -> FastMCP:
      """Converts an ADK agent into a FastMCP server."""

---

6. Java Streamable HTTP Remote Parameters

• Doc File: docs/tools-custom/mcp-deployment.md
• Claim: ADK Java uses StreamableHttpServerParameters.builder().url(...).headers(...).build() to configure remote Streamable HTTP MCP connections.
• Repository Proof:
  • Class Definition: google/adk-java/core/src/main/java/com/google/adk/tools/mcp/StreamableHttpServerParameters.java:33-40

    public class StreamableHttpServerParameters {
      private final String url;
      private final Map<String, String> headers;
      private final Duration timeout;

---

7. Kotlin Config-Driven Toolset & Header Provider

• Doc File: docs/tools-custom/mcp-deployment.md
• Claim: ADK Kotlin creates McpToolset via McpToolset.McpToolsetConfig(streamableHttpConnectionParams = ...).toToolset(headerProvider = ...).
• Repository Proof:
  • Factory Method: google/adk-kotlin/core/src/jvmMain/kotlin/com/google/adk/kt/tools/mcp/McpToolset.kt:406-425

        @JvmOverloads
        fun toToolset(
          headerProvider: (suspend (ReadonlyContext) -> Map<String, String>)? = null,
          progressConsumers: List<(McpSchema.ProgressNotification) -> Unit> = emptyList(),
        ): McpToolset {
          val params =
            listOfNotNull(stdioConnectionParams, sseConnectionParams, streamableHttpConnectionParams)
    
          require(params.size == 1) {
            "Exactly one of stdioConnectionParams, sseConnectionParams or streamableHttpConnectionParams must be set"
          }

---

Conclusion

All critical claims and code implementations across the 5 files in PR #2081 directly match the API definitions and conventions of their respective language repositories. The documentation PR is PASS.

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