1. Model Description

Gemini TTS generates speech from text (and optional multimodal inputs), with invocation methods being Vertex generateContent (synchronous) and streamGenerateContent (SSE streaming).

2. Billing

2.1 Platform Billing Items and Usage

chargeItemCode	Chinese Name	Usage Calculation (User Side)	Trigger Interface
in_token	input token	Response usageMetadata.promptTokenCount	Four TTS interfaces
out_token_audio	output audio tokens	Sum of tokens with modality equal to AUDIOin the usageMetadata.candidatesTokensDetails of the response	Four TTS interfaces

3. Details of Functional Interfaces

3.0 Common Request Body (Shared by Four Interfaces)

Content-Type: application/json. The body is a Vertex GenerateContentRequest JSON (either camelCase or snake_case is acceptable, consistent with the official specification).

Main Fields

Parameter Name	Field Type	Required or not	Description
contents	array / object	Yes	The content of the current conversation with the model. For single-turn queries, this is a single instance. For multi-turn queries, this is a repeated field that contains the conversation history and the latest request.
generationConfig	object	No	Generate configuration settings. In TTS scenarios, the commonly used component is speechConfig (for voice timbre, language, etc.).
systemInstruction	object	No	Applicable to gemini-2.0-flash and gemini-2.0-flash-lite. For instructions on guiding the model to achieve better performance. Text strings count towards the token limit. The role field of systemInstruction will be ignored and will not affect the model's performance.
safetySettings	array	No	Settings for each request, used to block unsafe content. Enforced on GenerateContentResponse.candidates.
tools	array	No	A piece of code that enables the system to interact with external systems to perform an action or a set of actions outside the scope and knowledge of the model.
toolConfig	object	No	Please refer to function calls.
cachedContent	string	No	The name of the cached content used as context to serve the prediction. Format: projects/{project}/locations/{location}/cachedContents/{cachedContent}
labels	object	No	You can add metadata to API calls in the Attribute–Value Pair format.

generationConfig.speechConfig (commonly used for TTS)

Parameter Name	Field Type	Required or not	Description
voiceConfig	object	No	Preset timbre configuration (for the structure, refer to the Google TTS / Gemini voice documentation).
multiSpeakerVoiceConfig	object	No	Multi-speaker voice configuration.
languageCode	string	No	Language code (e. g. en-US).

Common Response Fields (Synchronous / Streaming Single Chunk)

Parameter Name	Field Type	Description
candidates	array	Candidate results generated by the model; TTS audio is usually located at candidates[]. content.parts[]. inlineData (base64 audio).
usageMetadata	object	Token usage; includes promptTokenCount, candidatesTokenCount, candidatesTokensDetails, etc.
modelVersion	string	The model and version used for generation.
responseId	string	Response ID.
promptFeedback	object	Provide feedback related to prompts (e. g., security interceptions).

---

3.1 Synchronous generateContent (Platform Path)

3.1.1 Request URL

POST https://genaiapi-m2.cloudsway.net/v1/ai/{YOUR_ENDPOINT}/tts/generateContent

3.1.2 Request Body Parameters

See §3.0.

3.1.3 Response Parameters

See §3.0 Public Response Fields. When the HTTP status code is 200, the body is a complete GenerateContentResponseJSON object.

3.1.4 Request Example

curl --location 'https://genaiapi-m2.cloudsway.net/v1/ai/{YOUR_ENDPOINT}/tts/generateContent' \
--header 'Authorization: Bearer {YOUR_AK}' \
--header 'Content-Type: application/json' \
--data '{
  "contents": [{
    "role": "user",
    "parts": [{ "text": "Say hello in a friendly tone." }]
  }],
  "generationConfig": {
    "speechConfig": {
      "voiceConfig": {
        "voice": "Kore"
      }
    }
  }
}'

3.1.5 Response Example (Excerpt)

{
  "candidates": [{
    "content": {
      "parts": [{
        "inlineData": {
          "mimeType": "audio/L16;codec=pcm;rate=24000",
          "data": "<base64-audio>"
        }
      }]
    }
  }],
  "usageMetadata": {
    "promptTokenCount": 12,
    "candidatesTokenCount": 85,
    "candidatesTokensDetails": [
      { "modality": "AUDIO", "tokenCount": 80 }
    ]
  }
}

---

3.2 Streaming streamGenerateContent (Platform Path)

3.2.1 Request URL

POST https://genaiapi-m2.cloudsway.net/v1/ai/{YOUR_ENDPOINT}/tts/streamGenerateContent

Optional Query:

Parameter Name	Field Type	Required or not	Description
alt	string	No	When set to sse, Servlet SSE (text/event-stream) is used for write-back to adapt to some HTTP Clients; when omitted, a reactive SSE stream (text/event-stream) is returned.

3.2.2 Request Body Parameters

See §3.0.

3.2.3 Response Description

• Content-Type：text/event-stream

• The data of each event is aGenerateContentResponse JSON (some implementations may add a leading space before the JSON, please trim it during parsing).

• On error, the stream may end after pushing a JSON containing the errorfield.

• The usage shall be based on the last event containing usageMetadata (see §2.2).

3.2.4 Request Example

curl --location 'https://genaiapi-m2.cloudsway.net/v1/ai/{YOUR_ENDPOINT}/tts/streamGenerateContent?alt=sse' \
--header 'Authorization: Bearer {YOUR_AK}' \
--header 'Content-Type: application/json' \
--header 'Accept: text/event-stream' \
--data '{
  "contents": [{
    "role": "user",
    "parts": [{ "text": "Stream this sentence as speech." }]
  }],
  "generationConfig": {
    "speechConfig": {
      "voiceConfig": {
          "voice": "Kore"
      }
    }
  }
}'

---

3.3 Synchronous generateContent (Native Vertex Path)

3.3.1 Request URL

POST https://genaiapi-m2.cloudsway.net/{YOUR_ENDPOINT}/tts/v1beta1/publishers/google/models/{modelName}:generateContent

Path parameter{modelName}: Consistent with the Google model resource name (e. g. gemini-2.5-flash-preview-tts), it is recommended to be the same as the official model configured for the endpoint.

3.3.2 Request Body / Response

Same as §3.1 (for Body, see §3.0).

3.3.3 Request Example

curl --location 'https://genaiapi-m2.cloudsway.net/{YOUR_ENDPOINT}/tts/v1beta1/publishers/google/models/gemini-2.5-flash-preview-tts:generateContent' \
--header 'Authorization: Bearer {YOUR_AK}' \
--header 'Content-Type: application/json' \
--data '{
  "contents": [{
    "role": "user",
    "parts": [{ "text": "Hello." }]
  }],
  "generationConfig": {
    "speechConfig": {
      "voiceConfig": {
          "voice": "Kore"
      }
    }
  }
}'

---

3.4 Streaming streamGenerateContent (Native Vertex Path)

3.4.1 Request URL

POST https://genaiapi-m2.cloudsway.net/{YOUR_ENDPOINT}/tts/v1beta1/publishers/google/models/{modelName}:streamGenerateContent

3.4.2 Request Body / Response

Body is the same as §3.0; the response is SSE (text/event-stream), with the semantics identical to §3.2.3 (the native path currently writes back via SSE).

3.4.3 Request Example

curl --location 'https://genaiapi-m2.cloudsway.net/{YOUR_ENDPOINT}/tts/v1beta1/publishers/google/models/gemini-2.5-flash-preview-tts:streamGenerateContent' \
--header 'Authorization: Bearer {YOUR_AK}' \
--header 'Content-Type: application/json' \
--header 'Accept: text/event-stream' \
--data '{
  "contents": [{
    "role": "user",
    "parts": [{ "text": "Hello." }]
  }],
  "generationConfig": {
    "speechConfig": {
      "voiceConfig": {
          "voice": "Kore"
      }
    }
  }
}'