Sierra review

Sierra targets large brands that want a custom AI agent that sounds like them across every channel. Its Ghostwriter tool builds a production agent from uploaded SOPs, call transcripts, whiteboard photos or audio recordings, or from a plain English description, with guardrails built in. A single agent can run on voice, chat, email, WhatsApp, SMS and ChatGPT in 59 languages. Sierra puts weight on improving agents after launch: Explorer answers questions about performance from conversation data, Monitors flag conversations that need attention, Experiments run multivariate tests, and observability shows every tool call and knowledge lookup. Sierra pioneered outcome-based pricing, where you pay when the software achieves agreed outcomes, but it publishes no prices and sells through sales conversations. That makes it a poor fit for small teams and harder to compare on cost with self-serve tools.

Who it is for

Large consumer brands that want a custom, on-brand AI agent across voice, chat, email and WhatsApp.

Price

See vendor pricing (USD check pending).

US price check pending. See the vendor pricing page.

Key features

• Ghostwriter builds an agent from SOPs, transcripts, photos, audio or a plain English description
• One agent across voice, chat, email, WhatsApp, SMS and ChatGPT
• 59 languages, available 24/7/365
• Explorer, Monitors and Experiments for analyzing and testing agent performance
• Observability into tool calls, knowledge lookups and latency

Strengths and weaknesses

• Strength: Outcome-based pricing, paying only when set outcomes are achieved
• Strength: Agents can be built with or without engineering support
• Strength: Multivariate testing of conversation design
• Weakness: No published prices
• Weakness: Aimed at large companies, not small teams
• Weakness: Outcome definitions must be negotiated in the contract

Key facts

• Pricing model: Outcome-based, through sales
• Languages: 59
• Channels: Voice, chat, email, WhatsApp, SMS and ChatGPT
• Agent builder: Ghostwriter

Where it ranks

Sierra is No. 9 in our Best AI Customer Service Chatbots verdict.