Build with SIMRelay
A clean HTTP API, signed webhooks, an MCP server, and SDK quickstarts. Everything you need to build SMS-aware applications and agents.
Everything visible in the SIMRelay dashboard is also available via API: provisioning numbers, sending and receiving SMS, managing teams, subscribing to webhooks, configuring integrations. Authentication is standard Bearer tokens (API keys with scoped permissions). Webhook signatures are HMAC-SHA256. The API is versioned, the changelog is honest about breaking changes, and we'll send you a heads-up email before deprecating anything you depend on.
API reference
Every endpoint, parameter, and response field for the SIMRelay HTTP API.
Learn moreWebhooks
Subscribe to inbound SMS, delivery, and lifecycle events. Includes HMAC signature verification.
Learn moreChangelog
Release notes, breaking changes, and deprecations for the SIMRelay API and platform.
Learn moreDocumentation
Quickstart guides, authentication, error handling, and the conceptual model behind SIMRelay.
Learn more