# Dynamic Tool Registry

Dynamic Tool Registry lets your Flutter app expose app-specific MCP tools/resources at runtime, without rebuilding the MCP server.

## Why It Exists

Built-in MCP tools are generic. Real projects usually need custom actions like:

- inspect app state that only your code understands
- run domain-specific debug checks
- expose read-only app snapshots to the AI assistant

Dynamic registry exists so these capabilities can live in the Flutter app (where context and access control already exist), while still being callable through MCP.

## When To Use It

Use Dynamic Tool Registry when:

- you need app-specific diagnostics beyond built-in tools
- you have repeated debugging workflows worth turning into tools
- your project has internal state/config that should be exposed in a controlled shape

Do not use it when:

- built-in tools (`get_vm`, `get_app_errors`, `get_view_details`) already solve the need
- the action should run in production user builds
- the handler would perform risky side effects without explicit safeguards

## Architecture (ASCII)

```text
+---------------------+          stdio MCP           +---------------------------+
| AI Client           | <--------------------------> | mcp_server_dart           |
| (Cursor/Cline/etc.) |                              | - static tools            |
+---------------------+                              | - dynamic registry bridge |
                                                     +-------------+-------------+
                                                                   |
                                                     VM Service + DTD events
                                                                   |
                                                     +-------------v-------------+
                                                     | Flutter App               |
                                                     | + mcp_toolkit             |
                                                     | + MCPToolkitBinding       |
                                                     +---------------------------+
```

## Lifecycle (ASCII)

```text
App start
  |
  | MCPToolkitBinding.initialize()
  | MCPToolkitBinding.initializeFlutterToolkit()
  v
Register entries with addEntries(...)
  |
  v
Server discovers dynamic entries via VM/DTD
  |
  v
AI calls fmt_list_client_tools_and_resources
  |
  +--> fmt_client_tool(toolName, arguments)
  |
  +--> fmt_client_resource(resourceUri)
```

## Minimal Correct Setup

```dart
import 'dart:async';

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:mcp_toolkit/mcp_toolkit.dart';

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  MCPToolkitBinding.instance
    ..initialize()
    ..initializeFlutterToolkit();

  if (kDebugMode) {
    await registerDynamicEntries();
  }

  runApp(const MyApp());
}
```

## Register A Dynamic Tool

```dart
import 'package:dart_mcp/client.dart';
import 'package:mcp_toolkit/mcp_toolkit.dart';

Future<void> registerDynamicEntries() async {
  final sayHello = MCPCallEntry.tool(
    handler: (request) {
      final name = request['name'] ?? 'World';
      return MCPCallResult(
        message: 'Hello, $name!',
        parameters: {'greeting': 'Hello, $name!'},
      );
    },
    definition: MCPToolDefinition(
      name: 'say_hello',
      description: 'Return a greeting for a provided name',
      inputSchema: ObjectSchema(
        properties: {
          'name': StringSchema(description: 'Name to greet'),
        },
      ),
    ),
  );

  await MCPToolkitBinding.instance.addEntries(entries: {sayHello});
}
```

## Register A Dynamic Resource

`MCPResourceDefinition` is name-based. URI is derived from `name`:

- `app_config` -> `visual://localhost/app/config`
- `user_debug_state` -> `visual://localhost/user/debug/state`

```dart
import 'package:mcp_toolkit/mcp_toolkit.dart';

Future<void> registerConfigResource() async {
  final appConfig = MCPCallEntry.resource(
    handler: (_) => MCPCallResult(
      message: 'App configuration snapshot',
      parameters: {
        'config': {'apiBaseUrl': 'https://example.com'},
      },
    ),
    definition: MCPResourceDefinition(
      name: 'app_config',
      description: 'Read current app configuration',
      mimeType: 'application/json',
    ),
  );

  await MCPToolkitBinding.instance.addEntries(entries: {appConfig});
}
```

## How To Use It From AI Clients

1. Discover currently registered dynamic entries:

```json
{
  "name": "fmt_list_client_tools_and_resources",
  "arguments": {}
}
```

2. Execute by exact tool name:

```json
{
  "name": "fmt_client_tool",
  "arguments": {
    "toolName": "say_hello",
    "arguments": {"name": "Anton"}
  }
}
```

3. Read by exact resource URI:

```json
{
  "name": "fmt_client_resource",
  "arguments": {
    "resourceUri": "visual://localhost/app/config"
  }
}
```

## Multi-App / Multi-Target Correctness

If multiple debug targets are running, dynamic calls may return `connection_selection_required`.

Retry with explicit nested `connection`:

```json
{
  "name": "fmt_client_tool",
  "arguments": {
    "toolName": "say_hello",
    "arguments": {"name": "Anton"},
    "connection": {
      "targetId": "ws://127.0.0.1:59490/<token>/ws"
    }
  }
}
```

Connection fields supported:

- `targetId` (preferred, full VM websocket URI)
- `mode` (`auto`, `manual`, `uri`)
- `host`
- `port`
- `uri`
- `forceReconnect`

## Use It Correctly

Rules that prevent most issues:

- register entries only after `initialize()` has run
- keep names stable (`snake_case`) and unique
- always provide clear `description` and strict `inputSchema`
- keep handlers deterministic and response payloads compact
- return structured JSON in `parameters` for machine use
- guard debug-only tools with `kDebugMode`
- avoid hidden side effects; make destructive actions explicit in name/description

## Common Mistakes

| Symptom | Likely cause | Fix |
| --- | --- | --- |
| Tool/resource not visible | Entry not registered or client cached old tool list | Ensure `addEntries(...)` executes, then reload MCP server/client if needed |
| `tool not found` | Name mismatch | Copy exact `toolName` from `fmt_list_client_tools_and_resources` |
| `resource not found` | URI mismatch | Copy exact `resourceUri` from `fmt_list_client_tools_and_resources` |
| `connection_selection_required` | Multiple debug targets | Retry with `arguments.connection.targetId` |
| Unexpectedly large responses | Handler returns verbose payload | Return summary fields and only required details |

## Quick Checklist

- [ ] `MCPToolkitBinding.instance.initialize()` is called
- [ ] `initializeFlutterToolkit()` is called (if needed)
- [ ] dynamic entries are registered via `addEntries(...)`
- [ ] names/descriptions/schemas are explicit
- [ ] dynamic entries are verified via `fmt_list_client_tools_and_resources`
- [ ] multi-target retries include explicit `connection.targetId`
