Messagebird

The core messaging path is the Conversations API: create a conversation, then send messages to it across channels. This abstraction is cleaner than per-channel APIs but adds a conceptual layer agents must understand. The older Messages API (direct SMS) still works and is simpler for SMS-only use cases. REST API with JSON payloads throughout. Webhooks deliver inbound messages and delivery status updates — agents need a callback URL. The Numbers API manages phone number purchasing and assignment. The new Bird platform introduces Connectors and Flows with a different API surface. Pagination uses limit/offset on most list endpoints. API versioning is not explicit in URLs, which can cause confusion during platform transitions.

API errors return JSON with errors[] array containing code, description, and parameter fields — structured and actionable. HTTP status codes follow conventions: 401 for auth, 422 for validation, 429 for rate limits. SMS delivery reports arrive via webhook with status updates (delivered, failed, expired). WhatsApp message statuses follow a state machine (sent → delivered → read). Rate limits are account-level and documented per API endpoint. The main error handling consideration for agents: delivery confirmation is asynchronous across all channels. Agents that need to confirm delivery must implement webhook handlers and correlate by message ID. International SMS has inherent delivery uncertainty — some carriers don't return delivery receipts.

MessageBird (now Bird) offers omnichannel messaging across SMS, WhatsApp, Telegram, email, and voice through a unified API. For agents orchestrating multi-channel communications, the Conversations API provides a single interface to send and receive messages across channels without managing per-channel logic. The Flow Builder adds visual automation workflows that agents can trigger via API. WhatsApp Business API support is mature, including template messaging and interactive messages. The recent rebrand from MessageBird to Bird has created a documentation split — some resources are at developers.messagebird.com, others at docs.bird.com — which adds friction for agents trying to find authoritative references. Pricing is competitive for European and Asian markets where MessageBird has strong carrier relationships.

REST API uses API key authentication via Authorization: AccessKey header. Keys are created in the dashboard with limited scoping — full access or restricted to specific products. No OAuth support. Live and test API keys are separate, enabling sandbox testing without affecting production. The new Bird platform uses organization-scoped API keys with workspace isolation. For WhatsApp Business API, additional channel-level configuration is required in the dashboard. No temporary credential or token rotation mechanism. WebSocket connections for real-time messaging use the same API key. The authentication model is simple but lacks the granularity that agents managing multiple communication workflows might need — no per-channel or per-number permission scoping.

The rebrand from MessageBird to Bird has fractured the documentation landscape. Legacy docs at developers.messagebird.com are comprehensive for the REST API, SMS, and Conversations. New docs at docs.bird.com cover the Bird platform with Connectors and Flows. Agents must determine which API surface they're targeting and find the corresponding docs — there's no unified guide. Server SDKs (Node, Python, Go, PHP, Ruby, Java) are available under the MessageBird GitHub org but vary in maintenance status. The REST API reference is well-structured with curl examples. Getting started guides exist for each channel. Community and ecosystem are smaller than Twilio's. For agents starting fresh, the Bird platform docs are the recommended path, but the MessageBird REST API is more battle-tested.