# Backend Design: ECR-028 ToolDefinition

| ID | BD-2026-028 |
| Status | Approved |
| Coding | Loop authorized |
| Level | L2 |
| Migration | YES 000029 |

## Backend Change Boundary

```text
Domain: ToolDefinition (read)
App: AdminHandler → admin.Service → AdminRepo
API: GET /admin/ai/tools; GET /admin/ai/tools/{id}
Permission: admin.ai_config.read
Migration: 000029
```

## Out of boundary

工具在线编辑 · 运行时绑定 · UGC · 真支付

Rollback: down migration + remove routes/UI