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Gemini TTS provides the voice that speaks your agent’s responses. It takes a style prompt — plain-language direction for how lines should be delivered.

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What you need

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Getting a service-account JSON

  1. In the Google Cloud Console, select or create a project.
  2. Enable the Cloud Text-to-Speech API on it.
  3. Go to IAM & Admin → Service Accounts and create one.
  4. Open its Keys tab, choose Add Key → Create new key, and select JSON.
  5. The file downloads once. Store it securely and treat it as a secret.
Upload the whole file, including private_key and client_email.

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Adding the connection

  1. Go to Connections and choose Gemini TTS.
  2. Use Upload JSON to attach the service-account file.
  3. Save.

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What you can select afterwards

Choose your model on Model Configurations. Model — use a flash model on calls. pro is slower and the delay is audible to the caller. See Google’s speech generation models. Voice — Kore is the default. Google’s voice list describes how each one sounds. Language — see Google’s speech generation models for current coverage. Style prompt — optional. Describes delivery, for example Speak warmly and unhurriedly, like a receptionist who is not in a rush. Shapes tone, pace, and accent for the whole call. Blank gives the default delivery. Region — optional server region, such as us-central1. Set per workflow, not on the connection.

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Which Google voice connection to use

Each is a separate connection with its own credential.

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Troubleshooting

Gemini TTS does not accept one. An AI Studio key drives the language model and belongs on the Gemini connection.
Enable the Cloud Text-to-Speech API on the service account’s project. Without it the credential saves and the call fails.
It must be the JSON file, not P12, and the whole file rather than one field from it.