Loops

REST API at app.loops.so/api/v1/. Contact management: POST /v1/contacts/create, PUT /v1/contacts/update, GET /v1/contacts/find with email lookup. Contact properties are custom key-value pairs. Event sending: POST /v1/events/send with email, eventName, and optional eventProperties — this triggers any automation loops configured for that event. Transactional email: POST /v1/transactional with transactionalId (template ID), email, and dataVariables for dynamic content. Mailing list management: POST /v1/contacts/create with mailingLists object. The API surface is intentionally minimal — fewer than 10 endpoints. No batch contact operations. No campaign creation or analytics via API (dashboard only). The simplicity is the design philosophy: agents handle contact and event data, Loops handles email delivery and automation.

API errors return JSON with success (boolean) and message. Standard HTTP status codes. Rate limits: 10 requests per second. 429 responses indicate rate limiting. Contact creation returns errors for duplicate emails (409 Conflict). Event processing is async — the API accepts the event and returns success, but automation loop execution happens in the background. This means agents can't know immediately if an event triggered a loop. Transactional email sending returns delivery status but not inbox placement. The event-based model means reliability depends on correct event naming — a typo in the event name means the loop never triggers. No webhook notifications from Loops back to agents (one-way event flow). For agents, the main reliability pattern: validate event names against configured loops before sending.

Loops is a modern email platform specifically designed for SaaS companies — combining transactional email, marketing campaigns, and event-based automation in a single tool. For agents, the key capability is the event-based automation system: agents fire events (user.signed_up, trial.started, feature.activated) and Loops triggers automated email sequences (loops) based on those events. The API covers contact management, event sending, transactional email, and mailing list operations. Contact properties enable rich segmentation. Transactional emails support dynamic data injection. The platform is intentionally simpler than Mailchimp or HubSpot — focused on product-led SaaS email workflows. For agents building user lifecycle communications (onboarding sequences, feature adoption nudges, churn prevention), Loops' event-driven model is well-aligned.

API key authentication via Authorization: Bearer header. Keys are generated in Loops settings. Single key per workspace with full API access — no scoping. No OAuth for third-party integrations. No test mode keys — agents should use test contacts or a separate workspace for development. The auth model is the simplest possible: one key, full access. For agents, this means fast setup but no permission boundaries. No IP restrictions. No key expiry. Key rotation requires generating a new key and updating all integrations. For agents integrating Loops into a single product, the simplicity works. For multi-tenant agents or marketplace integrations, the lack of OAuth and scoping is limiting.

API documentation at loops.so/docs/api is clean and complete for the small API surface. Each endpoint has parameters, examples, and error descriptions. The getting started guide covers API key creation, contact management, and event sending in a linear flow. The documentation positions Loops' use cases clearly: onboarding sequences, product announcements, changelog updates, and lifecycle automation. Integration guides for popular frameworks (Next.js, Remix) show practical patterns. No official SDKs — the API is simple enough that raw HTTP is common. The documentation's main value: it explains when to use events vs. transactional email vs. campaigns, which helps agents choose the right pattern. For agents, the event sending and transactional email docs are the key starting points.