diff --git a/documentation/BOOTSTRAP__AI_Agent_Quickstart.md b/documentation/BOOTSTRAP__AI_Agent_Quickstart.md
index 9982ff53..ff86ddb5 100644
--- a/documentation/BOOTSTRAP__AI_Agent_Quickstart.md
+++ b/documentation/BOOTSTRAP__AI_Agent_Quickstart.md
@@ -336,7 +336,40 @@ src/routes/
 
 ---
 
-## 9. Reading Order for Deeper Dives
+## 9. Agent Messaging (ae_send_message / ae_inbox)
+
+Use MCP tools to coordinate with other agents — do not write directly to the inbox directories.
+
+```ts
+// Send a message to the backend agent
+ae_send_message({ recipient: 'backend', sender: 'frontend', content: '...' })
+
+// Check your inbox (reads from frontend_svelte/ by default in this project)
+ae_inbox({ command: 'list', status: 'unread' })
+```
+
+### Valid `ae_send_message` recipient names
+
+| Recipient name | Inbox directory | Agent |
+| --- | --- | --- |
+| `frontend` | `~/agents_sync/inbox/frontend_svelte/` | SvelteKit frontend agent (this agent) |
+| `backend` | `~/agents_sync/inbox/backend_fastapi/` | FastAPI backend agent |
+| `mcp_agent` | `~/agents_sync/inbox/mcp_agent/` | MCP/orchestration agent |
+| `scott_wks` | `~/agents_sync/inbox/scott_wks/` | Scott's workstation |
+| `scott_lpt` | `~/agents_sync/inbox/scott_lpt/` | Scott's laptop |
+| `gemini_cli` | `~/agents_sync/inbox/gemini_cli/` | Gemini CLI agent |
+
+> **Gotcha:** The inbox directory names (`frontend_svelte`, `backend_fastapi`) do NOT match the
+> `ae_send_message` recipient names (`frontend`, `backend`). Always use the recipient names above —
+> using the directory name will produce an `invalid choice` error.
+
+### Checking your own inbox
+
+The `ae_inbox` MCP tool reads from the `frontend_svelte` inbox by default when invoked in this project directory. Use `status='unread'` to see new messages, `status='all'` to see everything. New messages can also arrive as files in `~/agents_sync/inbox/frontend_svelte/` — check there if `ae_inbox` shows nothing but the user says a message was sent.
+
+---
+
+## 10. Reading Order for Deeper Dives
 
 Start here, then go deeper as needed: