Make your first AI phone call with a voice API
Place a call with Hail's voice API, give the agent a narrow task, and inspect the call status before deciding what happens next.
Hail / voice
Voice API for AI phone agents
Give your AI agent a real phone number. Make outbound calls, answer incoming calls, and bring the result back to your application through the API, MCP, or CLI.
A phone call with a job to do
A customer asks for a callback. Your application passes the number and instructions to Hail. The voice agent makes the call, and your application can inspect the outcome and transcript before taking the next step.
Use it for requested callbacks, appointment confirmations, or a conversation your agent cannot finish over text. Keep the task specific: who is calling, what needs to be answered, and when the agent should stop.
Connect your agent to the phone network
- Outbound calls: start a call with a destination, instructions, and an optional opening message.
- Inbound calls: configure a voice-capable number and the instructions for the agent that answers it.
- Your model and voice: use the configured voice stack or connect your own OpenAI-compatible model endpoint.
- Call results: inspect progress, the final status, and transcripts through the API and subscribed events.
A queued call is still in progress. Handle busy numbers, unanswered calls, and failures explicitly instead of treating every accepted request as a successful conversation.
Start with one call you can listen to
- Create a Hail account, add credits, and configure your calling number.
- Choose the API for your backend, MCP for your agent, or the CLI for a script.
- Call your own phone with a narrow task. Review the transcript and outcome before expanding the workflow.
The first-call tutorial walks through the request and the result. For a cost estimate, use the voice agent cost calculator and check Hail's current rates.
Follow up on another channel
When a call needs a written follow-up, use the SMS API or email API from the same Hail account. Your application decides what to send and when, based on the outcome of the call.