fix: remove --validate flag and add enterprise MCP guidance in step 17 (#1400)

Author: github-actions[bot]

workshop/17-add-mcp-tools.md

@@ -54,6 +54,20 @@ tools:
 > [!NOTE]
 > The `github` tool entry tells gh-aw to start the GitHub MCP server in proxy mode. The agent can then call GitHub tools — listing issues, fetching commits, reading file contents — scoped to the permissions you've declared above.
 
+<!-- -->
+
+> [!NOTE]
+> <details>
+> <summary><b>Enterprise users (GHEC, GHES, EMU): confirm MCP proxy availability before continuing.</b></summary>
+>
+> `mode: gh-proxy` routes all GitHub tool calls through the `GITHUB_TOKEN` that Actions provides automatically — no extra credentials or setup needed on github.com or GHEC.
+>
+> On GHES, the GitHub MCP server is supported from GHES 3.16+. If your instance is older, the `tools:` block will compile without errors but the agent's tool calls will fail at runtime. Verify your GHES version and confirm with your admin that the Copilot MCP proxy feature is enabled for your organization.
+>
+> If MCP is unavailable in your environment, the [Connect a Live Data Source](16-connect-data-source.md) step covers an alternative approach using deterministic shell steps that only require `GITHUB_TOKEN` and the `gh` CLI — no MCP server needed.
+>
+> </details>
+
 ### Reference the tools in your task brief
 
 Below the frontmatter, update the task brief to tell the agent it can use the MCP tools:
@@ -73,7 +87,7 @@ The agent will read this brief, decide which MCP tool calls to make, and weave t
 If you're working locally, compile before pushing:
 
 ```bash
-gh aw compile --validate
+gh aw compile
 ```
 
 <details>