write-adapter

name	write-adapter
description	Guide to implementing a custom transport adapter, platform emitter, or native bridge wrapper for IntentCall. Use when an agent needs to publish registry-backed intents to a new protocol or platform surface.
license	MIT
type	developer
metadata	{"author":"intentcall","version":"1.0.0","category":"intentcall"}

Write a Custom Adapter in IntentCall

Learn how to connect the IntentCall registry to a target surface. Runtime adapters execute AgentRegistry entries directly. Platform emitters generate metadata or source artifacts. Native bridge wrappers should collect parameters, authorize the source, and dispatch an invocation envelope back to Dart.

1. Implement AgentAdapter

All adapters must implement the AgentAdapter interface from intentcall_core.

import 'dart:async';
import 'package:intentcall_core/intentcall_core.dart';

class MyCustomAdapter implements AgentAdapter {
  MyCustomAdapter({required this.myTransportClient});

  final MyTransportClient myTransportClient;
  StreamSubscription<AgentRegistryEvent>? _subscription;

  @override
  String get id => 'my_custom_transport';

  @override
  bool get watchesRegistry => true;

  @override
  Future<void> attach(AgentRegistry registry) async {
    // 1. Publish all currently registered intents
    for (final entry in registry.listEntries()) {
      _publishIntent(registry, entry);
    }

    // 2. Listen to registry events to sync runtime registrations
    _subscription = registry.events.listen((event) {
      switch (event) {
        case IntentRegistered(:final qualifiedName):
          final intent = registry.get(qualifiedName);
          if (intent != null) {
            _publishIntent(
              registry,
              AgentRegistryEntry(
                key: qualifiedName,
                intent: intent,
              ),
            );
          }
        case IntentUnregistered(:final qualifiedName):
          _unpublishIntent(qualifiedName);
      }
    });
  }

  @override
  Future<void> detach() async {
    await _subscription?.cancel();
    _subscription = null;
  }

  void _publishIntent(AgentRegistry registry, AgentRegistryEntry entry) {
    final descriptor = entry.descriptor;
    myTransportClient.registerTool(
      name: entry.key,
      description: descriptor.description,
      inputSchema: descriptor.inputSchema,
      handler: (arguments) async {
        // Delegate execution to the core registry
        final result = await registry.invoke(entry.key, arguments);
        return <String, Object?>{
          'ok': result.ok,
          'message': result.message,
          if (result.ok) ...result.data,
          if (!result.ok) 'code': result.code,
          if (!result.ok) 'details': result.details,
        };
      },
    );
  }

  void _unpublishIntent(String name) {
    myTransportClient.unregisterTool(name);
  }
}

---

2. Key Rules for Adapter Authors

1. Keep it thin: The adapter should only map protocol structures to and from the AgentRegistry. It should never implement domain logic or custom validations that differ from the core registry validation.
2. Preserve registry keys: Use AgentRegistry.listEntries() for adapter publication. listDescriptors() is compatibility sugar for display-only catalog reads and can lose override-key intent.
3. Listen to Events: If watchesRegistry is true, ensure you handle both IntentRegistered and IntentUnregistered events in real-time to support hot-sync environments such as WebMCP.
4. Gate native/fallback sources: Fallback invoke paths and native bridge wrappers should use IntentCallAuthorizationPolicy; plain deep links are untrusted unless generated wrappers or app allowlists mark the source as trusted. Production registrations should use explicit source/name allowlists or confirmation callbacks. debugAllowAll() is for local dogfood only: it opens while assertions are enabled and denies in compiled profile/release builds.
5. Use Stable Wire Contracts: Depend on intentcall_schema rather than intentcall_core for sharing data envelopes (AgentResult / AgentCallEntry) between packages.

---

3. After Changing an Adapter

Add or extend a contract test using verifyNativeAdapterContract(...) from intentcall_testing. The canonical package entrypoint is packages/intentcall_testing/README.md.

Then run:

steward benchmark --scenario intentcall.adapter-contract --json

For smaller local checks, start with:

steward probe --json --profile quick

---

Related Documents

• DESIGN_FAQ.mdx — Adapter modularity details.
• DX_FAQ.mdx — Sibling overrides and testing custom adapters.
• intentcall_testing README — Contract-test entrypoint.