# Guides: phone numbers for AI agents

Step-by-step guides for developers who connect AI agents to real phone numbers.

- [How to give your AI agent a phone number](https://numberforagents.com/guides/how-to-give-your-ai-agent-a-phone-number): A practical guide to provisioning a real phone line for an AI agent: API steps, webhooks, compliance basics, and how to connect your voice stack.
- [AI agent SMS API explained](https://numberforagents.com/guides/ai-agent-sms-api-explained): Learn how SMS APIs work for AI agents: sending, receiving, webhooks, threading, delivery receipts, and design patterns for conversational text agents.
- [How AI voice agents receive phone calls](https://numberforagents.com/guides/how-ai-voice-agents-receive-phone-calls): Understand inbound call flow for AI agents: webhooks, SIP, WebSocket media, latency, handoff to humans, and how to bring your own voice stack.
- [How to connect a phone number to Vapi](https://numberforagents.com/guides/connect-phone-number-to-vapi): Put a phone number on a Vapi assistant: free Vapi number, Twilio import, Telnyx import, BYO SIP trunk, and the POST /phone-number API call.
- [How to connect a phone number to Retell AI](https://numberforagents.com/guides/connect-phone-number-to-retell-ai): Connect a phone number to a Retell AI agent: buy a Retell number, or bring your own Twilio or Telnyx number over SIP trunking. Plus SMS setup and costs.
- [How to give Claude or any MCP agent a phone number](https://numberforagents.com/guides/give-claude-mcp-agent-a-phone-number): Give Claude Code, Claude Desktop, or any MCP agent a real phone number. Telephony MCP servers compared, with install commands and safety rules.
- [A2P 10DLC registration for AI agents](https://numberforagents.com/guides/a2p-10dlc-registration-for-ai-agents): Register an AI agent's SMS number for A2P 10DLC: brand types, use cases, 2026 fees, approval time, toll-free vs 10DLC, and why campaigns get rejected.