How to configure stable multilingual agents (IT/EN/ES/FR/DE) with 2–3 languages per agent?

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Hi @insegne.video

  1. Set the language parameter to multi for multilingual agents. This enables auto-detection and code-switching between languages. For more details you can see (Set language for your agent - Retell AI). The language setting controls ASR (speech-to-text) and influences TTS pronunciation, but it does not enforce response language — you must do that in the prompt.

  2. For Prompt Design, Yes, explicitly instruct the agent in the prompt to only respond in the configured languages, You have to set that in the prompt yourself. This can be as easy as adding something like ‘always respond in Spanish’ into the prompt.

  3. Text normalization (normalize_for_speech) currently only supports English, Spanish, French, and German. Italian is not supported for normalization, so numbers/dates may occasionally be read incorrectly in Italian. For more details you can see (Normalize text for speech - Retell AI).

  4. The multi option exists for code-switching, a single multilingual agent per number is a supported approach. Limiting to 2–3 languages via prompt instructions is a reasonable strategy to reduce ASR drift.

  5. All your languages (IT/EN/ES/FR/DE) are supported by ElevenLabs, Cartesia, and MiniMax. Choose a voice that sounds natural in your primary language.

Thank You