Google Gemini GenerateContent

POST/v1beta/models/{model}:generateContent

Send a native Gemini request and receive a Gemini-compatible response. Use streamGenerateContent for streaming.

Path parameters

stringmodelrequired

Bare Google model name, such as gemini-3.5-flash. SandBase resolves it as google/{model}.

Request body

Optional<array>contents

Gemini conversation contents made of role and parts.

Optional<object>systemInstruction

Text system instruction in Gemini Content form.

Optional<object>generationConfig

Sampling, output length, structured output, and thinking settings.

Optional<array>tools

Function declarations or supported Gemini built-in tool configuration.

Optional<object>toolConfig

Gemini function-calling policy.

Optional<array>safetySettings

Gemini safety categories and thresholds.

Optional<string>cachedContent

Gemini cached-content resource passed through when supported.

curl -X POST \
  "https://api.sandbase.ai/v1beta/models/gemini-3.5-flash:generateContent" \
  -H "x-goog-api-key: $SANDBASE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"contents":[{"role":"user","parts":[{"text":"Explain immutable infrastructure in one sentence."}]}]}'

Response200 OK

{
  "candidates": [
    {
      "content": {
        "role": "model",
        "parts": [
          {
            "text": "Immutable infrastructure replaces servers from versioned images instead of modifying them in place."
          }
        ]
      },
      "finishReason": "STOP",
      "index": 0
    }
  ],
  "usageMetadata": {
    "promptTokenCount": 8,
    "candidatesTokenCount": 15,
    "totalTokenCount": 23
  }
}

Authentication

Google-compatible requests can carry the SandBase API key in x-goog-api-key, Authorization: Bearer …, or the key query parameter, in that priority order. Prefer a header: query-string credentials can appear in proxy logs and browser history.

Streaming

Replace the method suffix with :streamGenerateContent. Without a query parameter, SandBase returns Google-compatible response objects as a streamed JSON array. Add ?alt=sse for Server-Sent Events:

curl -N -X POST \
  "https://api.sandbase.ai/v1beta/models/gemini-3.5-flash:streamGenerateContent?alt=sse" \
  -H "x-goog-api-key: $SANDBASE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"contents":[{"role":"user","parts":[{"text":"Write a short greeting."}]}]}'

Native image generation

These image models have dedicated native GenerateContent mappings:

• Gemini 3 Pro Image（Nano Banana Pro）
• Gemini 3.1 Flash Image（Nano Banana 2）

For these mappings, SandBase forwards the request and response payloads without converting them through Chat Completions. This preserves image parts, response modalities, and provider-defined fields. Use the bare model name in the URL; for example, google/gemini-3.1-flash-image becomes gemini-3.1-flash-image in the path.

Routing and translation boundaries

SandBase selects only providers that support the requested native Gemini protocol. If the selected model has no compatible native mapping, the request fails instead of falling back to a provider with a different protocol.

Models that use the translated GenerateContent path support text, function calls and responses, inline image/* data, and public HTTP(S) image references. That translated path rejects unsupported inline MIME types, private Google Files or gs:// references, multiple candidates, and unsupported response modalities with a Google-style 400 INVALID_ARGUMENT response. The image-generation mappings listed above use raw passthrough and are not subject to those translation-only limits; validate the returned media fields according to the selected provider's response.