# AI Agent Tools With Usage-Based Pricing

> Source: https://theagentsindex.com/collections/ai-agent-tools-with-usage-based-pricing (curated, quality-gated, re-verified)

"Usage-based" sounds like the transparent option: pay only for what you use, and calculate your own cost before you sign up. That holds for all but four of these 22 tools, which publish an actual number you can price your own usage against: [Vapi](/vapi) at $0.05/minute, [Bland AI](/bland-ai) at $0.14/minute, [Intercom Fin](/intercom-fin) at $0.99/resolution, [OpenAI Realtime API](/openai-realtime-api) at $32/$64 per million audio tokens, [Webhound](/webhound) from $1 for a narrow research check. That is a real rate card in every case, whatever the unit. [Devin](/devin) sells the meter as a unit budget rather than a per-minute rate: a free tier, then Pro at $20/month and Max at $200/month, all billed by the Agent Compute Unit the work actually consumes.

It breaks for the other four. [Sierra](/sierra), [Decagon](/decagon), [Ada](/ada) and [PolyAI](/polyai) each state their pricing model in the abstract, as "outcome-based," "per minute" or "per conversation," then list "Custom" where the actual number should be; none publishes a rate card or offers self-serve signup, and independent purchase-data estimates (not vendor figures) are the only cost signal available for any of the four.

The free-tier split tracks this same divide closely: [Manus](/manus), [ElevenLabs Conversational AI](/elevenlabs-conversational-ai) and [Genspark](/genspark), 3 of these 22, let you run real usage at $0 before paying anything, and all three sit in the public-rate group. None of the sales-led, custom-quoted tools offers any free tier or self-serve path at all.

By category, the filter bites hardest in [support agents](/category/support-agents): 8 of 14 bill by usage, the highest share of any category here, and support is where the outcome-based, sales-quoted pattern concentrates. [Voice agents](/category/voice-agents) contribute the same number of entries from a larger pool, 10 of 23, where per-minute billing is close to the category default. [Research & data agents](/category/research-agents) add 3 of 13, and [coding agents](/category/coding-agents) 2 of 28.

| Name | What it is | Why it's here | Pricing | API |
| --- | --- | --- | --- | --- |
| [Vapi](https://theagentsindex.com/vapi.md) | Developer platform for building, testing and deploying voice AI agents that make and receive phone calls. | $0.05/min pay-as-you-go orchestration fee, with the underlying model, voice and telephony billed through on top; about $10 in free trial credits, no permanent free tier. | — | Yes |
| [Retell AI](https://theagentsindex.com/retell-ai.md) | Pay-as-you-go platform for building, testing and running AI phone, chat and SMS agents. | $0.07-$0.31/min pay-as-you-go, with $10 in free credits and 20 free concurrent calls to start, but no permanent free tier. | — | Yes |
| [Bland](https://theagentsindex.com/bland-ai.md) | Enterprise voice AI platform for inbound and outbound phone agents, running on Bland's own self-hosted models. | $0.14/min with a $0 platform fee and no card required to start, but no permanent free tier once the starting credits run out. | — | Yes |
| [ElevenLabs Agents](https://theagentsindex.com/elevenlabs-conversational-ai.md) | Hosted platform for building voice and chat agents, with telephony, SDKs and a choice of LLM. | The one usage-based voice tool here with an ongoing free tier: 15 call minutes/month at $0, then LLM and telephony usage billed separately on top. | — | Yes |
| [Sierra](https://theagentsindex.com/sierra.md) | Enterprise platform for customer-service AI agents across voice, chat, email and messaging, priced by outcome. | Priced entirely on outcomes, a pre-negotiated rate per resolved issue, but that rate is never published; Sierra states pricing as 'Custom' with no self-serve option or free tier at all. | — | Yes |
| [Fin](https://theagentsindex.com/intercom-fin.md) | Intercom's customer agent that resolves support conversations across chat, email, voice and social channels. | $0.99 per outcome across any helpdesk with a 50-outcome monthly minimum; the Pro add-on (Operator + analytics) starts at $99/month with usage tiers above 1,000 conversations, and the Fin API Platform is gated to $250k+ annual spend. | — | Yes |
| [Decagon](https://theagentsindex.com/decagon.md) | Enterprise platform for building and running AI customer-support agents across chat, voice and email. | No public price list; Vendr purchase-data puts the median annual contract at $386,000: independent estimates, not an official Decagon figure. | — | Yes |
| [Crescendo](https://theagentsindex.com/crescendo.md) | AI-native CX platform: agents resolving support across voice, chat, email and SMS, with a staffed team behind them. | Priced per resolution from $2.99 with a 'Total Outcome Guarantee' (no charge for unresolved conversations), but no public self-serve tier; engagement starts with a paid pilot. | — | Yes |
| [Cresta](https://theagentsindex.com/cresta.md) | Enterprise contact-centre platform with autonomous voice and digital AI agents plus real-time human agent assist. | Sales-led custom enterprise quote per deployment; the only public price is Agent Assist on AWS Marketplace at $150,000/year for one channel (125,000 chats OR 100,000 calls, non-cancellable, non-refundable), with no published per-call or per-chat overage rate. | — | Yes |
| [Ada](https://theagentsindex.com/ada.md) | Enterprise customer-service AI agent platform spanning voice, messaging and email with tool-based actions. | No published price list; Vendr purchase-data analysis puts the median contract at $73,500/year, with independent estimates ranging roughly $30K to $300K+/year by volume. | — | Yes |
| [PolyAI](https://theagentsindex.com/polyai.md) | Enterprise platform for building voice and chat agents that resolve customer calls, priced per minute. | Per-minute pricing bundling tuning, maintenance and support, per PolyAI's own pricing page, but the rate itself is never published; third-party estimates put typical contracts around $150,000/year and up. | — | Yes |
| [Synthflow](https://theagentsindex.com/synthflow-ai.md) | Enterprise voice AI platform with in-house telephony for inbound and outbound call automation. | $0.11-$0.16/min typical, billed as three separate components (voice engine, LLM, telephony); no permanent free tier. | — | Yes |
| [Genspark](https://theagentsindex.com/genspark.md) | All-in-one AI workspace with autonomous agents for slides, docs, sheets, code, media and scheduled automation. | Free tier included: about 100 credits/day refreshed daily with no card required, before its Super Agent workspace bills further usage. | — | Yes |
| [Webhound](https://theagentsindex.com/webhound.md) | Budget-capped autonomous web research returning cited reports, datasets and machine-readable claims via MCP or API. | Priced per dollar of compute with no subscription: roughly $1 for a narrow check, $5 for a standard cited report, scaling up from there; a one-time $5 free credit for new accounts. | — | Yes |
| [Zendesk AI agents](https://theagentsindex.com/zendesk-ai-agents.md) | Customer-service AI agents for messaging, email and voice, billed per automated resolution. | Per-seat plan from $55/agent/month with the Essential AI Agent tier included, then a published overage of $1.50 per Automated Resolution on a committed plan or $2.00 pay-as-you-go above the plan allowance. | — | Yes |
| [OpenAI Realtime API](https://theagentsindex.com/openai-realtime-api.md) | OpenAI's speech-to-speech API for low-latency voice agents over WebRTC, WebSocket or SIP. | Billed purely on audio tokens with no platform fee: $32/$64 per 1M tokens for the flagship model, working out to an independently estimated $0.06-$0.11/min in production once caching is in effect. | — | Yes |
| [Deepgram Voice Agent API](https://theagentsindex.com/deepgram-voice-agent-api.md) | One WebSocket API that runs speech-to-text, LLM orchestration and text-to-speech for real-time voice agents. | Pay-as-you-go rates from $0.050/min (Custom, bring-your-own LLM and TTS) up to $0.163/min (Advanced with Deepgram's own STT and TTS), with promotional cuts through September 12, 2026; a flat $4.50/hr on the Standard tier, a one-time $200 new-account credit, and Flux TTS free inside Voice Agent through the same window. | — | Yes |
| [Cartesia](https://theagentsindex.com/cartesia.md) | Real-time speech models and a managed runtime for production phone and web voice agents. | $0.06/min for Line voice-agent minutes plus $0.014/min for Cartesia telephony, on top of a monthly Sonic TTS and Ink STT credit pool: a hybrid model with a published per-minute rate regardless of tier. | — | Yes |
| [Auto-Respond](https://theagentsindex.com/auto-respond.md) | AI answering service and voice agent that answers calls and marketplace texts, qualifies leads and books jobs. | A $10/month voice number plus $1/minute of talk time, alongside separate flat monthly fees per channel (Facebook, Thumbtack, Yelp): a mixed usage-and-subscription structure, not a pure per-minute rate. | — | Yes |
| [Muse Code](https://theagentsindex.com/muse-code.md) | Meta's terminal and CI coding agent, built on the Muse Spark model. | $1.25/M input and $4.25/M output tokens on the Standard tier, or a steep discount on the Contributor tier in exchange for letting it train on your code. | — | Yes |
| [Devin](https://theagentsindex.com/devin.md) | Cloud AI software engineer that takes a ticket, works in its own VM, and opens a pull request. | Free tier available, plus Pro at $20/month and Max at $200/month, billed by the Agent Compute Unit (ACU) the work actually consumes; Teams from $80/month with full seats at $40 each, and unlimited seats on every plan. | — | Yes |
| [Manus](https://theagentsindex.com/manus.md) | General-purpose AI agent that plans and executes multi-step tasks on its own cloud computer. | Free tier included: about 300 daily refresh credits, roughly one task a day, before paid usage kicks in. | — | Yes |

## How this list is built

A tool earns a place here if its own Published, sourced listing records `attributes.pricingModel` as `usage-based`: billed by a metered unit (minutes, resolutions, tokens, dollars of compute) rather than a flat per-seat subscription or one-time fee. Within that set, each entry's own `pricingTiers` data was read directly for whether the vendor publishes an actual per-unit number a buyer could use to estimate cost before signing up, or states the pricing model without the rate (`priceDisplay: 'Custom'`, sales-led only, no self-serve signup), and separately whether an ongoing $0 tier exists (a limited free trial or one-time signup credit does not count as a free tier). Every number cited is the listing's own already-researched, sourced figure; where a figure is a third-party estimate rather than the vendor's own published number, the entry says so explicitly, exactly as the source listing does.