Update custom tools README for subdirectory/index.ts structure

packages/coding-agent/examples/custom-tools/README.md

@@ -4,13 +4,15 @@ Example custom tools for pi-coding-agent.
 
 ## Examples
 
-### hello.ts
+Each example uses the `subdirectory/index.ts` structure required for tool discovery.
+
+### hello/
 Minimal example showing the basic structure of a custom tool.
 
-### question.ts
+### question/
 Demonstrates `pi.ui.select()` for asking the user questions with options.
 
-### todo.ts
+### todo/
 Full-featured example demonstrating:
 - `onSession` for state reconstruction from session history
 - Custom `renderCall` and `renderResult`
@@ -19,7 +21,8 @@ Full-featured example demonstrating:
 
 ### subagent/
 Delegate tasks to specialized subagents with isolated context windows. Includes:
-- `subagent.ts` - The custom tool (single, parallel, and chain modes)
+- `index.ts` - The custom tool (single, parallel, and chain modes)
+- `agents.ts` - Agent discovery helper
 - `agents/` - Sample agent definitions (scout, planner, reviewer, worker)
 - `commands/` - Workflow presets (/implement, /scout-and-plan, /implement-and-review)
 
@@ -28,11 +31,11 @@ See [subagent/README.md](subagent/README.md) for full documentation.
 ## Usage
 
 ```bash
-# Test directly
-pi --tool examples/custom-tools/todo.ts
+# Test directly (can point to any .ts file)
+pi --tool examples/custom-tools/todo/index.ts
 
-# Or copy to tools directory for persistent use
-cp todo.ts ~/.pi/agent/tools/
+# Or copy entire folder to tools directory for persistent use
+cp -r todo ~/.pi/agent/tools/
 ```
 
 Then in pi: