Tone is an open-source voice AI platform for building, deploying, and self-hosting voice agents. Agents can handle inbound and outbound calls, web widgets, or chat, combining prompts, tools, workflows, configurable models, voices, and speech-to-text providers. Its knowledge base can ingest PDFs, scraped documents, Notion, and Confluence content, with retrieval, re-ranking, citations, and custom vocabulary. A visual workflow builder supports branching, loops, human handoff, TypeScript hooks, and triggers from Zapier, REST API, or HighLevel. The test center runs simulated calls with different personas, accents, and edge cases, supports parallel regression runs, and replays production calls. Observability covers measures and signals such as latency, interruptions, sentiment, and real-time alerts. Developers can use a TypeScript-first SDK, CLI, hosted API, or self-host with Docker Compose and a Kubernetes Helm chart. Tone is MIT licensed and lists 29 supported languages. The Self-host plan is free; Cloud costs $0.09 per minute and includes $10 free credit with no card required.

Who it is for

Tone suits developers building voice agents for calls, web widgets, or chat, especially those needing workflow controls, testing, and call observability. It also serves teams that want self-hosting or a hosted API.

What is good

Free MIT-licensed self-host plan.
Supports inbound and outbound calls.
Includes human handoff in workflows.
Supports 29 languages.
Offers Docker Compose and Helm deployment.

What to know first

Cloud is billed at $0.09 per minute.
Enterprise pricing is custom and not listed.
Self-host customers receive community Discord support.

Verdict

Tone combines agent building, deployment, testing, and monitoring in one voice AI platform. Choose between free self-hosting, usage-priced Cloud, or custom Enterprise terms.

Tone plans and pricing

All plans

Self-host Free $0 Unlimited agents, calls, workflows · Bring your own LLM, voice, telephony · Docker Compose & Helm chart · Community Discord support · All integrations included trytone.ai · 30 Sept 2026

Cloud $0.09/mo $0.09 per minute $10 free credit, no card required · Auto-scaling worker fleet · 99.99% uptime SLA · SOC 2 Type II · HIPAA-ready · Email & chat support · Pay-as-you-go, cancel anytime trytone.ai · 30 Sept 2026

Enterprise Not published Custom Single-tenant or on-prem · BAA, DPA, custom contracts · Dedicated support and Slack channel · Custom integrations and roadmap · Audit logs, SSO/SAML, RBAC trytone.ai · 30 Sept 2026

Compared on AI voice agents

Free plan: Yes
Inbound calls: Yes
Outbound calls: Yes
Human handoff: Yes
Supported languages: 29 languages
Custom phone numbers: Yes

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The record

What it does

Tone is an open-source voice AI platform for building, deploying, and self-hosting voice agents.

Agent channels

Agents can run inbound, outbound, web-widget, or chat experiences.

Agent composition

Agents combine prompts, tools, workflows, configurable models, voices, and speech-to-text providers.

Knowledge base

Tone ingests PDFs, scraped documents, Notion, and Confluence content and provides chunking, embeddings, retrieval, re-ranking, citations, and custom vocabulary.

Workflow builder

The visual workflow builder supports branching, loops, human handoff, TypeScript hooks, and triggers from Zapier, REST API, or HighLevel.

Testing

The test center runs simulated calls with personas, accents, and edge cases, supports parallel regression runs, and replays production calls.

Observability

Observability includes interruption rate, latency, sentiment, gibberish detection, stereo recordings, waveform inspection, custom dashboards, and real-time alerts.

Self-hosting

Tone can be started with Docker Compose and includes a Kubernetes Helm chart, with Postgres, Redis, and ClickHouse in the example stack.

Open-source license

Tone is MIT licensed and its agent runtime, call routing, and evaluation harness are published on GitHub.

Security posture

The site states SOC 2 Type II, HIPAA-ready, and GDPR compliance, and the changelog says edge PII redaction and HMAC-SHA256 webhook signing were added.

Support

Self-host customers receive community Discord support, Cloud customers receive email and chat support, and Enterprise customers receive dedicated support with a Slack channel.

Performance

The product page states a 218 ms voice-loop p50, 120 ms time-to-first-byte, 10k+ concurrent calls per region, 29 supported languages, and a 99.99% Cloud uptime SLA.

Developer access

Tone provides a TypeScript-first SDK, CLI, local Docker development loop, composable runtime, and hosted API access.

Headquarters

Bengaluru and San Francisco

Price from

$0.09/mo