Overview

Tone supports inbound and outbound calls, web widgets, and chat, with human handoff when an interaction needs a person. Agents can combine prompts, tools, workflows, configurable models, voices, and speech-to-text providers. An MIT-licensed runtime, call routing, and evaluation harness are published on GitHub, alongside a TypeScript-first SDK, CLI, local Docker development loop, and hosted API.

Its knowledge base can ingest PDFs, scraped documents, Notion, and Confluence content, then apply chunking, embeddings, retrieval, re-ranking, citations, and custom vocabulary. This gives teams several ways to ground responses in their materials, while making source setup and retrieval choices part of the work.

Key features

Workflows, testing, and monitoring

The visual workflow builder supports branching, loops, TypeScript hooks, and triggers from Zapier, REST API, or HighLevel. The test center simulates calls with personas, accents, and edge cases, runs parallel regressions, and replays production calls. Together, these tools suit teams iterating on agent behavior rather than stopping at initial call setup.

Observability covers interruption rate, latency, sentiment, and gibberish detection, with stereo recordings, waveform inspection, custom dashboards, and real-time alerts. The product page states a 218 ms voice-loop p50, 120 ms time-to-first-byte, capacity for 10k+ concurrent calls per region, and support for 29 languages. These are useful operational claims for teams evaluating voice workloads, alongside a 99.99% Cloud uptime SLA.

Integrations and deployment

Integrations include OpenAI, Anthropic, Google Gemini, Mistral, Llama, ElevenLabs, Cartesia, PlayHT, Deepgram, Whisper, AssemblyAI, Twilio, Telnyx, Plivo, LiveKit, HubSpot, Salesforce, Zapier, n8n, Slack, Notion, Confluence, and GoHighLevel. Self-hosting starts with Docker Compose and includes a Kubernetes Helm chart; the example stack uses Postgres, Redis, and ClickHouse. That flexibility is valuable for technical teams, but self-hosted customers must bring their own LLM, voice, and telephony services.

Tone states SOC 2 Type II, HIPAA-ready, and GDPR compliance. Its changelog says edge PII redaction and HMAC-SHA256 webhook signing were added. These measures may matter to teams handling sensitive calls, while Enterprise adds audit logs, SSO/SAML, and RBAC.

Pricing

Self-host is 0.00 USD per free, billed $0. It includes unlimited agents, calls, and workflows; Docker Compose and Helm; all integrations; and community Discord support. You bring your own LLM, voice, and telephony, so the free platform does not remove the costs or configuration of those services. This is the clearest fit for teams prioritizing control and able to operate their own stack.

Cloud is 0.09 USD per month, billed $0.09 per minute. It includes $10 free credit with no card required, auto-scaling worker fleet, a 99.99% uptime SLA, SOC 2 Type II, HIPAA-ready status, email and chat support, and pay-as-you-go billing that can be cancelled anytime. The per-minute charge makes it a managed path without a fixed commitment, but ongoing call volume drives the bill.

Enterprise has custom pricing. It offers single-tenant or on-prem deployment, BAA and DPA, custom contracts, dedicated support with a Slack channel, custom integrations and roadmap, audit logs, SSO/SAML, and RBAC. It fits organizations needing deployment or governance arrangements beyond the self-host and Cloud tiers.

Platforms

Tone is available through API, self-hosted deployment, and web. Its Docker Compose and Kubernetes Helm options give self-hosting teams two stated deployment routes.

Who it's for

Tone is best suited to development teams building voice agents that need configurable models, workflows, and deployment choices, especially when testing and operational monitoring are part of the project. It is less suited to buyers seeking a turnkey managed service without per-minute charges or teams unable to supply and configure services for self-hosting.

Pros and cons

Pros: One platform spans agent composition, knowledge retrieval, workflow design, call simulation, and operational monitoring, giving technical teams tools across the agent lifecycle.
Pros: MIT-licensed runtime and self-host deployment options support teams that want control over hosting and integrations.
Pros: Cloud includes a $10 credit without a card requirement and can be cancelled anytime, allowing a limited-cost start.
Cons: Self-hosting requires teams to supply their own LLM, voice, and telephony services.
Cons: Cloud is billed at $0.09 per minute, so costs rise with usage rather than staying fixed.
Cons: Enterprise pricing is custom, which means buyers seeking that tier need a tailored commercial arrangement.

Alternatives

AI Voice Agents is the directory's broader category for comparing voice-agent options.

Choose LiveKit Agents if its Build plan's 1,000 agent session minutes, five concurrent sessions, or single deployment better fits a capped starting workload. Yellow.ai offers a free tier with one AI agent and 500/month included, making it an option for a smaller initial setup. Rapida AI is another freemium choice, with a Launch plan that brings your own STT, TTS, LLM, and SIP and includes 10-day observability retention.

Pipecat is a free alternative. Choose Deepgram Voice Agent API if a paid, pay-as-you-go voice agent API is a better fit; its Standard plan is 0.08 USD per month, or 0.07 USD per month with BYO TTS. Ring AI offers a free tier with 100 minutes per month for testing. Cognigy is a paid web option. Intervo is a freemium alternative with an MIT-licensed self-hosted plan.

Verdict

Choose Tone if you want an open-source voice-agent platform with serious tools for workflow design, evaluation, monitoring, and a choice between self-hosting and managed Cloud. Its main reason to look elsewhere is the operating trade-off: self-hosting means bringing your own AI and telephony services, while Cloud charges by the minute.

	Cognigy	Tone
Free plan	No	Yes
Free trial	No	Yes
Paid from	—	$0.09/mo
Open source	No	No
Platforms	api, self-hosted, Web	api, self-hosted, Web
Human handoff	Yes	Yes
Free plan	—	Yes
Inbound calls	—	Yes
Outbound calls	—	Yes
Supported languages	—	29 languages
Custom phone numbers	—	Yes

Cognigy vs Tone

Cognigy

Tone