PolyAI vs Sierra
Which Agents AI tool is better in 2026?
PolyAI
The world's most lifelike voice AI agents for enterprise customer service.
Sierra
Conversational AI agents for every business
Side-by-side
Sierra is the more established option (raised $2.2B); pricing is comparable on both sides.
| Metric | PolyAI | Sierra |
|---|---|---|
| Taglinei | The world's most lifelike voice AI agents for enterprise customer service. | Conversational AI agents for every business |
| Foundedi | 2017🏆 | 2023 |
| HQi | London, GB | San Francisco, US |
| Employeesi | 201-500🏆 | 100-200 |
| Neuron scorei | 70 | 89🏆 |
| Total fundingi | $120M | $2.2B🏆 |
| Latest roundi | Series C · May 2024 | Series D · May 2026 |
| Valuationi | — | $15.8B🏆 |
| Cheapest paid plani | — | — |
| Free plani | ✗ | ✗ |
| Free triali | ✓ | ✗ |
| Top tier pricei | Enterprise · Contact sales | Enterprise · Contact sales |
| Pricing summaryi | 1 published plans | 1 published plans |
| Categoriesi |
Capability matrix
Developer-facing capabilities and access signals for PolyAI and Sierra.
| Capability | PolyAI | Sierra |
|---|---|---|
| MCP support | ✗ | ✗ |
| Public API | ✗ | ✗ |
| Webhooks | ✗ | ✗ |
| OAuth 2.0 | ✗ | ✗ |
| SDK languages | 2 (JavaScript, Python) | — |
| Free plan | ✗ | ✗ |
| Free trial | ✓ | ✗ |
| Verified | ✗ | ✓ |
| Active deal | ✗ | ✗ |
🟢 Strengths of PolyAI
- Offers a free trial
- More mature (2017)
🔵 Strengths of Sierra
- Has raised more capital ($2.2B vs $120M)
- Higher Neuron score (89 vs 70)
- Newer company (2023)
- Verified profile
Which should you choose?
Choose Sierra if price matters most — it starts at Enterprise · Contact sales, which is friendlier for teams watching burn. Both AI Agents tools ship core features, so the cost delta often decides it for small teams and solo operators.
Choose Sierra if you want the most established option — it has raised $2.2B, suggesting more runway for enterprise features, support, and long-term roadmap. For mission-critical workflows or larger teams, that stability often outweighs a lower monthly price.
Frequently asked questions
PolyAI vs Sierra — which is better?
It depends on your priority. PolyAI is the leaner option; Sierra has broader feature depth. See the side-by-side table above.
Is PolyAI cheaper than Sierra?
No — Sierra's cheapest paid plan is Enterprise · Contact sales, while PolyAI's is Enterprise · Contact sales.
Do PolyAI and Sierra offer free plans?
PolyAI: Free trial only. Sierra: Paid only.
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