Decagon vs Sierra: which is better?
Neither is better across the board. Both are enterprise AI agent platforms sold through sales, with no public price list. The real differences are how they bill and how you build.
- Choose Decagon if you want predictable per-conversation billing, CX teams editing Agent Operating Procedures (AOPs) in natural language with Git-based versioning for engineers, and AI voice in 70+ languages, including outbound calls.
- Choose Sierra if you want to pay on outcomes (resolutions, saved cancellations, upsells), build in code with the Agent SDK or without code in Agent Studio, and reach customers on chat, SMS, WhatsApp, email, voice and ChatGPT.
- Consider a third option if you are not an enterprise contact center: Aftersales Agent has published pricing, $0.99 per resolution, and a helpdesk for your human team in the same product. See the third option.
How do Decagon and Sierra compare side by side?
On paper the two look alike. Both build branded AI agents for large consumer companies, both cover chat, email and voice, and both are quote-only. The table shows where they diverge.
| Feature | Decagon | Sierra |
|---|---|---|
| Best for | Enterprises that want per-conversation billing and CX-owned procedures | Large consumer brands that want outcome-based billing and a code or no-code build |
| Published prices | No; sales-led | No; sales-led |
| Pricing model | Per conversation (most customers) or a higher per-resolution rate | Outcome-based: pay when the agent completes a task; escalations usually not charged |
| How agents are built | AOPs: natural language plus code, Git-based versioning; Duet drafts AOPs from transcripts | Agent SDK for developers, Agent Studio for no-code teams, Ghostwriter builds agents from SOPs, transcripts or plain English |
| Channels | Chat, email, voice | Chat, SMS, WhatsApp, email, voice, ChatGPT |
| Voice languages | 70+ languages, own Chord speech model, outbound calling | 55+ languages, card and ACH payments over the phone |
| Testing | Experiments (A/B tests), simulations at scale, Watchtower QA | Simulations, debugging traces, Insights with Monitors and Experiments |
| Named integrations | Salesforce, Zendesk, Intercom, Kustomer, Amazon Connect, RingCentral, SIP, MCP, custom APIs | Secure actions into your systems, contact center handoff; data partners such as Snowflake, Databricks, AWS and Google Cloud |
| Security badges shown | SOC 2, ISO 27001, HIPAA, PCI DSS, GDPR, CCPA | SOC 2, ISO 27001, ISO 42001, HIPAA, PCI DSS, GDPR |
| Helpdesk for human agents | Not included; hands off to your helpdesk | Not included; hands off to your contact center |
| Customers they name | Chime, Duolingo, American Airlines, Oura | Rocket Mortgage, SiriusXM, Gap Inc., Vanguard |
Checked October 2026 on decagon.ai and sierra.ai. Neither vendor publishes prices; confirm current terms with each vendor.
What are the main differences between Decagon and Sierra?
Three things separate them: the billing unit, the build model and channel reach. AI quality is close enough that your own pilot should decide it, not a feature list.
1. Billing unit
Decagon charges per conversation by default. Its Decagon's pricing post says the majority of customers choose that model for predictability, and that a per-resolution option exists at a higher rate. Sierra charges per outcome. Its Sierra's outcome-based pricing post says outcomes can be resolved conversations, saved cancellations or upsells, and that escalated cases are in most cases not charged. In short: Decagon is easier to budget, Sierra moves more of the risk onto the vendor.
2. How you build and change the agent
Decagon's AOPs are written in natural language like an SOP, backed by code, with Git-based tracking for technical teams. Sierra splits the work in two: the Agent SDK lets developers build agents in their own environment and release cycle, and Agent Studio lets CX teams build and manage agents without code. Sierra's Ghostwriter can draft an agent from SOPs, transcripts or a plain-English description; Decagon's Duet drafts AOPs from transcripts.
3. Channels and voice
Both run AI on the phone. Decagon's voice product lists 70+ languages, its own Chord speech model and outbound calling. Sierra's voice agent lists 55+ languages and taking card and ACH payments on the call without an IVR handoff. Sierra also lists SMS, WhatsApp and ChatGPT as channels on its home page; Decagon's home page lists voice, chat and email.
4. Integrations
Decagon's integrations page names helpdesks (Zendesk, Salesforce, Intercom, Kustomer) and telephony (Amazon Connect, RingCentral, SIP trunking), plus MCP and custom APIs. Sierra's public pages describe secure actions into your systems and contact center handoff rather than a long connector list. If your stack matters, ask each vendor to show your exact helpdesk and telephony setup in the demo.
Is Decagon or Sierra cheaper?
You cannot tell from their websites: neither publishes rates. What you can compare is the billing unit, and that decides which quote is cheaper at your resolution rate.
- Decagon per conversation: you pay for every conversation the AI handles, including ones it hands to a person. Cost per month = conversations × quoted rate.
- Decagon per resolution: a higher rate, charged only on resolved conversations.
- Sierra per outcome: you pay when the agent completes a defined outcome; escalations are usually free. Cost per month = outcomes × quoted rate, and outcomes can include revenue events such as saved cancellations.
Example: how to compare two quotes. Assume 50,000 conversations a month and a 60% resolution rate. A per-conversation quote of $X costs 50,000 × X. A per-outcome quote of $Y costs 30,000 × Y. The two are equal when Y = X ÷ 0.6, so a per-outcome rate is only more expensive if it is more than about 1.67 times the per-conversation rate. At a 40% resolution rate the break-even rises to 2.5 times. The lower your expected resolution rate, the more outcome pricing protects you.
Two more lines belong in the comparison. First, both products hand off to a helpdesk or contact center you still pay for separately. Second, ask each vendor how a "resolution" or "outcome" is defined and audited; our guide to measuring resolution rate lists the questions to ask.
Want a price you can see today?Aftersales lists every plan on its pricing page: Agent is $0.99 per resolution, and conversations it can't help with are free.
Should your team pick Decagon or Sierra?
Pick by team type and by how you want to pay.
| Team type | Better fit | Why |
|---|---|---|
| Finance team wants a fixed, forecastable AI bill | Decagon | Per-conversation pricing scales with volume, not with an outcome definition |
| You want the vendor to carry performance risk | Sierra | Outcome-based pricing; escalations usually not charged |
| Engineering wants agents in its own codebase and release cycle | Sierra | Agent SDK runs in your existing development environment |
| CX leads want to own and edit procedures daily | Either | Decagon AOPs and Sierra Agent Studio both target non-engineers |
| Voice-first contact center with outbound calls | Decagon | Outbound calling and 70+ voice languages listed |
| Payments taken on the phone | Sierra | Card and ACH collection over voice without IVR handoff |
| WhatsApp, SMS or ChatGPT as key channels | Sierra | Listed as native channels |
| Helpdesk on Intercom or Kustomer, telephony on Amazon Connect or RingCentral | Decagon | Named on its integrations page |
| Small or mid-market team, no budget for an enterprise deployment | Neither | See the third option below |
Whichever you shortlist, run a pilot on a slice of real traffic and grade transcripts yourself before signing a multi-year contract.
Is there a third option to Decagon and Sierra?
Yes. If you want an AI agent that resolves conversations and takes actions but do not want a sales-led enterprise deployment, Aftersales is the third option. It publishes its prices, bills only resolutions and includes the helpdesk your human team works in.
- Published pricing. Free plan, then Starter $24, Growth $69 and Scale $109 per seat per month billed annually. Agent costs $0.99 per resolution on every plan, counted once per conversation however many questions it contained. Conversations Agent can't help with are free, and Agent never needs a seat.
- Procedures in plain language. Describe a procedure or import an existing macro and Agent turns it into steps. Each step maps to a connector or API with explicit, revocable permissions, with spend limits and escalation on sentiment, keywords, customer tier or legal language.
- Actions built in. Shopify order lookup, verification and replacements, Stripe refunds and Salesforce; other systems connect through the Aftersales API or webhooks.
- AI and people in one place. Inbox covers email, chat, WhatsApp, SMS, phone and social. When Agent hands off, the rep sees the conversation, the data Agent looked up and what it already tried. Copilot drafts replies that cite their sources.
- Or keep your helpdesk. Agent on its own runs inside Zendesk, Salesforce Service Cloud or Freshdesk with no seats and no migration, at $0.99 per resolution with a minimum monthly commitment.
- Quality on every conversation. Insights runs Monitors across all conversations and reports cost per conversation in one unit.
Agent reaches a median 71% resolution after 90 days, and Northwind Outdoors cut cost per conversation by 41%. Security covers a GDPR DPA, US hosting and HIPAA support with a signed BAA on the Enterprise plan.
Example cost. Assumptions: 20,000 conversations a month, Agent resolves 60%, 10 human reps on Growth, list prices, annual billing. Resolutions: 12,000 × $0.99 = $11,880. Seats: 10 × $69 = $690. Total $12,570 a month including the helpdesk, or $11,880 for Agent on its own inside your existing helpdesk (minimum commitment applies). The 8,000 handed-off conversations cost nothing on the Agent side.
Where Decagon or Sierra is still the better pick: Aftersales does not list an AI voice agent (its phone features are for your human team), Agent covers 31 languages against their 55+ and 70+ voice languages, and it does not list ISO 27001 or PCI DSS. If AI phone calls, outbound campaigns or those certifications are requirements, stay with Decagon or Sierra. Compare more options on our Decagon alternatives and Sierra alternatives pages, the alternatives hub and our roundup of the best AI customer service software.