 Open-source realtime media infrastructure with the Agents framework, SIP, and phone numbers MCPOpenAPIllms.txt | realtime+4 | MCP+2 | — | api-key, Messaging | 5/5 | | |
 Email API for developers with React Email, batch sending, and an official MCP server MCPOpenAPIllms.txt | email+3 | MCP+2 | — | api-key, Messaging | 5/5 | | |
 Voice agent platform handling telephony, turn-taking, interruptions, and warm transfers MCPOpenAPIllms.txt | voice-agents+3 | MCP+2 | — | api-key, Messaging | 5/5 | | |
 Notification infrastructure API — workflows, preferences, and multi-channel delivery for agent output MCPOpenAPIllms.txt | notifications+2 | MCP+2 | — | api-key, Messaging | 4/5 | | |
 Transactional email with high deliverability and detailed delivery webhooks OpenAPIllms.txt | email+2 | OpenAPI+1 | — | api-key, Messaging | 4/5 | | |
 Managed phone agents with conversation design, simulation testing, and production monitoring OpenAPIllms.txt | voice-agents+3 | OpenAPI+1 | — | api-key, Messaging | 4/5 | | |
 Email delivery and marketing API by Twilio OpenAPI | email+2 | OpenAPI | — | api-key, Messaging | 4/5 | | |
 SMS, voice, WhatsApp, and verification APIs, with an official MCP server over the platform MCPOpenAPIllms.txt | sms+4 | MCP+2 | — | api-key, Messaging | 4/5 | | |
 Hosted realtime channels and WebSocket delivery OpenAPI | realtime+2 | OpenAPI | — | api-key, Messaging | 3/5 | | |