Grow2.ai has shipped Polish-speaking agents for four pilots. The cost line for "native-speaker tone work" is ~€340 per language per pilot — about 3 hours of an experienced native speaker, plus 2 hours of Iryna's editor time. It's the smallest line item on the engagement budget. It is also, by our own measurement, the highest-leverage one.
The before/after CSAT delta
On Atlas Rentals (84 units, Kraków), we shipped a v1 of the Polish agent with no native-speaker pass — Iryna wrote the prompt directly from a structured description of the brand voice. CSAT on Polish guests for the first 7 days: 4.1 / 5. We then ran the 3-hour native-speaker pass with Magdalena — Atlas's Polish front-desk lead — and re-shipped on Day 8. CSAT for the next 14 days on Polish guests: 4.6 / 5.
Same agent. Same retrieval. Same model. The delta is voice. €340 well spent.
What changes in the prompt, concretely
The before-and-after, on the same guest-arrival message:
- v1 (no pass): "Witam serdecznie. Państwa apartament jest gotowy. Kod do skrzynki z kluczami: 4729. Hasło Wi-Fi: AtlasGuest2024. W razie pytań proszę pisać."
- v2 (after pass): "Cześć! Apartament jest gotowy, klucze w skrzynce — kod 4729. WiFi: AtlasGuest2024 (znajdziecie je też na lodówce). Jakby coś, jestem tu — 24/7. Miłego pobytu w Krakowie!"
The v1 is correct Polish. Magdalena read it and said "this sounds like a hotel in 2008". The v2 reads, to a Polish guest, like a host who knows their own apartment. The difference is informal-but-courteous register, the parenthetical hint about WiFi-on-fridge (which is the kind of thing only a real host knows to mention), and the "jakby coś" — which is untranslatable but signals warmth.
Why the cost is fixed, per language
Three hours of native-speaker time is enough to draft the per-language tone document, review it against five real conversation samples, and approve the v2 prompt. We have not found a workflow that takes less time and produces a working profile. We have not found a workflow that takes more time and produces a measurably better one.
The language doesn't matter to the cost. Polish, Italian, Romanian — same 3 hours, same €340 line item. What does matter: the native speaker has to be a person who actually does the work, not a translator. Magdalena answers Atlas guests for a living. A bilingual office worker without that context produces a profile that's linguistically clean and operationally useless.