Vapi

Overview

Vapi is a developer platform for building AI voice agents for phone and web calls. Assistants can also run as text chat over the Chat API, a web widget and SMS. SMS needs an imported Twilio number: inbound texts start a chat session with the assigned assistant, and voice assistants can send texts during calls with a built-in sms tool. SMS chat works only for US Twilio numbers, US to US, needs 10DLC approval, and only customers can start a conversation.

Key features

• Inbound SMS chat with session context kept for 24 hours by default
• Built-in sms tool for texts during calls
• Chat API with streaming and an OpenAI-compatible endpoint
• Vapi numbers, imported Twilio numbers and SIP trunks
• Squads of assistants with handoffs, tools, MCP and server webhooks

Pricing

Usage based: $0.05 a minute for Vapi hosting plus model, voice and transcription costs at provider rates, with $5 of free credit. Packages are Core at $29 a month, Pro at $999 a month minimum, and Premier custom. HIPAA costs $2,000 a month.

How it compares to Linq

Vapi texts over SMS only, with no iMessage and no RCS, and needs your own Twilio number for it. Linq supplies its own lines for iMessage, RCS and SMS and can start conversations, while Vapi's SMS agents cannot send the first message. Vapi places and answers AI calls, which Linq's API does not.

Best for

Developers building AI phone agents who want customers to text the same assistant on a US number.

Sources

• vapi.ai/pricing
• docs.vapi.ai/llms.txt
• docs.vapi.ai/chat/sms-chat.md
• docs.vapi.ai/phone-numbers/inbound-sms.md
• docs.vapi.ai/tools/default-tools.md
• docs.vapi.ai/chat/quickstart.md