# Choose an AI Phone Voice with the AgentLine API - **Canonical URL:** https://agentline.cloud/blog/agentline-voice-selection-api-guide - **HTML:** https://agentline.cloud/blog/agentline-voice-selection-api-guide - **Markdown:** https://agentline.cloud/blog/agentline-voice-selection-api-guide.md - **Date:** 2026-10-18 - **Updated:** 2026-10-18 - **Author:** Sameer Srivastava - **Read time:** 3 min read - **Tags:** `Voice`, `API`, `Guide`, `Vapi` > List live voice presets, set an agent's voice, override it for a test call, and understand account defaults and Vapi's provider-based configuration. --- To choose a voice for an AgentLine phone agent, read GET /v1/voices and set voice_id on the agent. For one outbound call, pass voice_id to POST /v1/calls. The override order is call, agent, account default, then system default. A saved agent voice therefore takes precedence over a changed account default. ## Read the available voices first The public catalog returns voices with preset_name, voice_id, name and description, plus default_voice_id. Use the live catalog as the authority rather than copying a voice UUID from an old tutorial. ```bash curl --fail-with-body https://api.agentline.cloud/v1/voices ``` On October 18, 2026, the catalog listed female-1 (Friendly Female), female-2 (Reassuring Female), female-3 (Guide Female), male-1 (Supportive Male), male-2 (Thinker Male), and male-3 (Helpful Male). These labels describe presets, not measured quality or suitability for every accent or language. ## Save a voice on your agent The following examples use Bash. Set AGENTLINE_API_KEY privately in your shell and replace AGENT_ID with an agent you own. This update changes the voice for subsequent calls; it does not start a call. ```bash curl --fail-with-body -X PATCH https://api.agentline.cloud/v1/agents/AGENT_ID -H "Authorization: Bearer $AGENTLINE_API_KEY" -H "Content-Type: application/json" -d '{"voice_id":"female-2"}' ``` To change the account fallback, PATCH /v1/account/voice with the same voice_id body. GET /v1/account/voice reads that setting. An explicit voice saved on an agent still wins. Invalid preset names or malformed voice UUIDs can produce a validation error; re-read the catalog before retrying. ## Compare two voices on your own phone Provision a number using the [API walkthrough](/blog/agentline-api-developer-walkthrough), then replace TEST_PHONE with your own E.164 number. This request places a paid call. Keep the prompt and greeting identical between tests so you are comparing voices rather than scripts. ```bash curl --fail-with-body -X POST https://api.agentline.cloud/v1/calls -H "Authorization: Bearer $AGENTLINE_API_KEY" -H "Content-Type: application/json" -d '{"agent_id":"AGENT_ID","to_number":"TEST_PHONE","voice_id":"male-1","initial_greeting":"Hello, this is an AI voice test. Please say a time and a street name."}' ``` Record the call ID, preset, prompt version and observations. Check pronunciation of names, dates and numbers, interruption handling, and whether short replies remain intelligible over an actual telephone connection. Read GET /v1/calls/{call_id} and its transcript after the call. A successful configuration response alone does not prove how the voice sounded to the listener. ## AgentLine and Vapi configuration AgentLine exposes a voice_id field with a hosted preset catalog. [Vapi's voice documentation](https://docs.vapi.ai/providers/voice/overview) describes a voice object with provider and voiceId, which suits developers choosing among voice providers. Do not copy a Vapi voice identifier into AgentLine and assume it names the same voice. Choose based on the control you need, then test your actual language and call conditions. Reviewed against [AgentLine API schema](https://api.agentline.cloud/openapi.json) and [agent skill](/skill.md). For the rest of the calling stack, see the [voice-calling guide](/blog/ai-agent-voice-calling-complete-guide). ## Frequently Asked Questions **How do I select an AI phone voice through an API?** On AgentLine, GET /v1/voices lists the current catalog. Set voice_id with PATCH /v1/agents/{id}, or supply voice_id to POST /v1/calls for one call. **Why did changing my account voice not change my agent?** An explicit agent voice overrides the account default. A per-call voice overrides both. Check all three settings before testing another call. **Does AgentLine let me choose any Vapi voice provider?** No. AgentLine uses its own hosted voice catalog. Vapi's provider and voiceId configuration is a separate API contract. --- ## Related guides - [Transfer an AI Phone Call to the Owner with AgentLine](https://agentline.cloud/blog/ai-call-transfer-to-owner-agentline) — also as markdown: https://agentline.cloud/blog/ai-call-transfer-to-owner-agentline.md - [AgentLine REST API: Calls, Numbers and Transcripts](https://agentline.cloud/blog/agentline-api-developer-walkthrough) — also as markdown: https://agentline.cloud/blog/agentline-api-developer-walkthrough.md - [Best API to Buy and Manage US Phone Numbers for an AI Calling App](https://agentline.cloud/blog/best-api-to-buy-us-phone-numbers-for-ai-calling-app) — also as markdown: https://agentline.cloud/blog/best-api-to-buy-us-phone-numbers-for-ai-calling-app.md ## About AgentLine AgentLine gives AI agents real phone numbers for voice and SMS. Docs: https://docs.agentline.cloud · Pricing: https://agentline.cloud/pricing · Skill: https://agentline.cloud/skill.md