docs(integrations): add Agent Guild endpoint preflight

docs/integrations/agent-guild.md

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+---
+catalog_title: Agent Guild
+catalog_description: Check agent endpoints and inspect pricing before delegation
+catalog_icon: /integrations/assets/agent-guild.svg
+catalog_tags: ["mcp"]
+---
+
+# Agent Guild MCP tool for ADK
+
+<div class="language-support-tag">
+  <span class="lst-supported">Supported in ADK</span><span class="lst-python">Python</span><span class="lst-typescript">TypeScript</span>
+</div>
+
+[Agent Guild](https://github.com/AgentTanuki/agent-guild) provides endpoint
+preflight, signed reputation evidence, and pricing discovery through a hosted
+MCP server. Connect it with ADK's MCP toolset to inspect an external agent before
+deciding whether to delegate work to it.
+
+## Use cases
+
+- **Inspect a delegation target**: Compare an endpoint's advertised capabilities
+  with the observations and unknowns returned by a live preflight.
+- **Check costs before use**: Retrieve current paid-operation prices, callable
+  entrypoints, and free alternatives before choosing a trust operation.
+- **Review evidence limits**: Keep unavailable checks and uncertainty visible
+  when explaining whether an endpoint is suitable for a task.
+
+## Prerequisites
+
+- Set up ADK and model access using the [Python](/get-started/python/) or
+  [TypeScript](/get-started/typescript/) quickstart.
+- Install MCP support for the language you use:
+
+    === "Python"
+
+        ```bash
+        pip install "google-adk[mcp]"
+        ```
+
+    === "TypeScript"
+
+        ```bash
+        npm install @google/adk "@modelcontextprotocol/sdk@^1.26.0"
+        ```
+
+The two tools in this example are free and require no Agent Guild account,
+API key, or wallet. Model-provider usage follows your model provider's pricing.
+Preflight sends the selected public endpoint URL to Agent Guild's hosted service,
+which probes that endpoint. Supply public URLs without embedded credentials.
+
+## Use with agent
+
+The tool filter exposes only endpoint preflight and pricing discovery. It does
+not expose registration, payment, or paid trust-read tools to the agent.
+
+=== "Python"
+
+    === "Remote MCP Server"
+
+        ```python
+        from google.adk.agents import Agent
+        from google.adk.tools.mcp_tool import McpToolset
+        from google.adk.tools.mcp_tool.mcp_session_manager import StreamableHTTPConnectionParams
+
+        root_agent = Agent(
+            model="gemini-flash-latest",
+            name="agent_guild_preflight",
+            instruction=(
+                "Inspect the public agent endpoint the user supplies before delegation. "
+                "Use guild_preflight and report its observations and unknowns. "
+                "Use guild_paid_operations when the user asks about trust-operation prices. "
+                "A preflight result is evidence, not a guarantee or permission to execute."
+            ),
+            tools=[
+                McpToolset(
+                    connection_params=StreamableHTTPConnectionParams(
+                        url="https://agent-guild-5d5r.onrender.com/mcp",
+                        timeout=30,
+                    ),
+                    tool_filter=["guild_preflight", "guild_paid_operations"],
+                )
+            ],
+        )
+        ```
+
+=== "TypeScript"
+
+    === "Remote MCP Server"
+
+        ```typescript
+        import { LlmAgent, MCPToolset } from "@google/adk";
+
+        const rootAgent = new LlmAgent({
+            model: "gemini-flash-latest",
+            name: "agent_guild_preflight",
+            instruction:
+                "Inspect the public agent endpoint the user supplies before delegation. " +
+                "Use guild_preflight and report its observations and unknowns. " +
+                "Use guild_paid_operations when the user asks about trust-operation prices. " +
+                "A preflight result is evidence, not a guarantee or permission to execute.",
+            tools: [
+                new MCPToolset(
+                    {
+                        type: "StreamableHTTPConnectionParams",
+                        url: "https://agent-guild-5d5r.onrender.com/mcp",
+                    },
+                    ["guild_preflight", "guild_paid_operations"],
+                ),
+            ],
+        });
+
+        export { rootAgent };
+        ```
+
+Run the agent using the quickstart for your language. For example, ask it to
+inspect a public agent endpoint you operate and explain which checks were
+inconclusive. Then ask which paid trust operations are available and what each
+currently costs.
+
+## Available tools
+
+Tool | Description
+---- | -----------
+`guild_preflight` | Probe a public agent endpoint and return observed capabilities, evidence, and unknowns. Free without a key.
+`guild_paid_operations` | List current paid-operation prices, entrypoints, settlement resources, and free alternatives. This discovery call is free.
+
+The server also offers signed Agent Passports and paid trust reads. These are
+outside this example's tool filter. A signature establishes origin and
+integrity, not the safety of an agent's messages or the quality of future work.
+Paid reads such as `guild_check` require the current payment terms or funded
+sandbox credits; do not treat them as free preflight calls.
+
+## Additional resources
+
+- [Agent Guild repository and API documentation](https://github.com/AgentTanuki/agent-guild)
+- [Agent Guild machine-readable service guide](https://agent-guild-5d5r.onrender.com/llms.txt)
+- [MCP tools in ADK](/tools-custom/mcp-tools/)