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Works with Gemini 2.5 · Vertex AIGive Gemini a voice
Callsy plugs into any Gemini-powered agent — Google AI Studio, Vertex AI, the Gemini API, or any framework that speaks function tools. 27 tools, 40+ languages, instant setup.
Listen to voices in every language Gemini speaks
50+ voices across 40+ languages — click any to hear a sample.
Why Gemini + Callsy
Gemini is fluent in 100+ languages
Now it can phone them
Gemini's multilingual reasoning is a superpower — and it's wasted if your agent can't reach customers in their language. Callsy ships 40+ production-quality voices across English, Spanish, French, German, Italian, Polish, Portuguese, Arabic, Hindi, Japanese, and more. Gemini reasons, Callsy calls.
Function calling + MCP
Two paths in: Google's native function tools schema, or direct MCP for Gemini clients that speak it.
Vertex AI ready
Use Callsy from Vertex AI's managed agent runtime — the tool schema loads once and reuses across projects.
Multimodal workflows
Gemini reads a customer email, detects their language, and calls them with the matching voice — in one turn.
EU hosting
Core data in AWS EU. Combine with Vertex AI's EU endpoints for end-to-end EU residency.
Setup
Register Callsy as a function tool
Gemini's function-calling schema takes functionDeclarations. Register any of Callsy's 27 tools — here's make_call:
// Register Callsy as a Gemini function tool
const callsyTool = {
functionDeclarations: [{
name: "callsy_make_call",
description: "Place a real outbound phone call.",
parameters: {
type: "OBJECT",
properties: {
agent_id: { type: "STRING" },
contact_phone: { type: "STRING" },
context: { type: "OBJECT" }
},
required: ["agent_id", "contact_phone"]
}
}]
};
const result = await model.generateContent({
contents: [{ role: "user", parts: [{ text: userPrompt }] }],
tools: [callsyTool]
});Gemini's strengths, applied
Multilingual calling, one prompt
Detect language, then call
“Read this customer's email and call them in their native language. Use the appropriate Callsy voice.”
Global cart recovery
“Every cart-abandoned contact in the last 48h: call them in their language with a 10% offer.”
Translated follow-ups
“Call each lead and summarize our proposal in their language, then email the English version.”
Long-context briefings
“Here's a 50-page deal doc. Call our account rep and walk them through the key risks before their meeting.”
Frequently asked
Which Gemini surfaces support Callsy?
Any Gemini model with function calling — Gemini 2.5 Pro, Gemini 2.5 Flash, Gemini Pro, and all Vertex AI Gemini deployments. Wire Callsy in as function tools, or use the MCP server if your Gemini client supports MCP.
Is this available on Google AI Studio?
Yes. Define the Callsy tools in your Studio system instructions, and the model will call them like any other function. Same on Vertex AI — register the schema once and reuse across projects.
Does Callsy cover Google's languages?
Yes — Callsy supports 40+ languages with studio-quality neural voices. That includes the languages Google emphasizes (English variants, Spanish, French, German, Italian, Portuguese, Hindi, Arabic, Japanese, Korean, Mandarin).
What about multimodal — can Gemini analyze call audio?
Callsy returns full transcripts with timestamps and optional recorded audio URLs. Your Gemini workflow can download the audio and pass it to Gemini's audio-understanding tools for sentiment, keyword spotting, or QA.
Is there a free tier?
Yes — 10 calls per month, no credit card required. Paid plans start at €15/month with 70% off for early bird.