flutter-mcp-toolkit-custom-tools

Custom MCP Toolkit Tools & Resources (Dynamic Registry)

Use this when bundled MCP tools (screenshot, semantic snapshot, tap, …) are not enough and you need app-specific read surfaces or actions — e.g. cart totals, feature flags, curated debug snapshots of internal state. Entries are registered in the Flutter process and exposed to the agent through the dynamic registry.

Migration: The legacy call-entry type was removed in intentcall Phase 6b. Use AgentCallEntry or mcpToolkitTool / mcpToolkitResource. See flutter-mcp-toolkit-intentcall-migration.

Boundary: Change app discovery, Flutter VM-service extensions, or app-owned debug surfaces here. Change canonical registry/session semantics, schema policy, platform projection, or publish behavior in the upstream IntentCall repository.

Pick the right primitive

Handler signatures

Native AgentCallEntry (preferred for new code)

Handlers receive AgentArguments (Map<String, Object?>) and return AgentResult:

import 'package:mcp_toolkit/mcp_toolkit.dart';

final tool = AgentCallEntry.tool(
  namespace: 'app',
  name: 'cart_get_snapshot',
  description: 'Return current cart total and items for a user.',
  inputSchema: const {
    'type': 'object',
    'additionalProperties': false,
    'properties': {
      'userId': {'type': 'string'},
    },
    'required': ['userId'],
  },
  handler: (final args) async {
    final userId = args['userId']?.toString() ?? '';
    final cart = CartRepository.instance.forUser(userId);
    return AgentResult.success(
      message: 'ok',
      data: {
        'total': cart.total,
        'items': cart.items.map((final i) => i.toJson()).toList(),
      },
    );
  },
);

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