Gemini 3.8 Flash

Gemini 3.8 Flash is Google’s generally available Flash model for long-horizon software engineering, autonomous agents, and complex multimodal workflows. Use the stable model ID gemini-3.8-flash with POST /v1beta/models/gemini-3.8-flash:generateContent.

Model specifications

Property	Value
Model ID	`gemini-3.8-flash`
Release stage	Generally available
Input	Text, image, video, audio, and PDF
Output	Text
Input token limit	1,048,576
Output token limit	65,536
Thinking levels	`low`, `medium`, `high`
Default thinking level	`medium`

Choose a workflow

Text and thinking
Multimodal understanding
Structured output
Function calling
Built-in tools

Send text in contents[].parts[].text. Use generationConfig.thinkingConfig.thinkingLevel to trade latency for reasoning depth.

Level	Recommended use
`low`	Latency-sensitive chat, drafting, and quick analysis
`medium`	General coding and agent workflows; this is the default
`high`	Difficult reasoning and multi-step tool orchestration

The final conversation turn must be a non-empty user turn. Do not prefill a response by ending the request with a model turn.

Combine text with images, audio, video, or PDF documents in the same contents request.

Use inlineData with mimeType and Base64-encoded data for inline media.
Use fileData with mimeType and fileUri for an accessible media or document URI.
Keep each media item inside the parts array for the turn that refers to it.
The model returns text; it does not generate image, audio, or video output.

Base64 encoding increases request size. Prefer fileData for large assets or files reused across requests.

Set generationConfig.responseMimeType to application/json and supply generationConfig.responseSchema to constrain the output.Use a focused schema with explicit required fields. The returned JSON is contained in a text part, so parse candidates[].content.parts[].text after checking finishReason.

Add functions under tools[].functionDeclarations. Control selection with toolConfig.functionCallingConfig.Supported modes are AUTO, ANY, NONE, and VALIDATED. Use allowedFunctionNames to restrict the callable subset.Preserve every thoughtSignature returned by the model when replaying conversation history. A functionResponse must include the function name; return the model-provided call id and your structured response when available.

Gemini 3.8 Flash can use the following built-in tools on the current endpoint:

Tool field	Purpose
`googleSearch`	Ground answers with current web results
`googleMaps`	Ground location answers with Google Maps data
`urlContext`	Read and analyze supplied web pages
`codeExecution`	Run model-generated code and return its result
`computerUse`	Propose browser actions; this capability is in Preview

Read the returned groundingMetadata, executableCode, codeExecutionResult, or tool-call parts instead of assuming every response contains only text.

Request examples

Text and thinking
Multimodal understanding
Structured output
Function calling
Built-in tools

cURL

curl "https://www.anyfast.ai/v1beta/models/gemini-3.8-flash:generateContent?key=YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [{
      "role": "user",
      "parts": [{"text": "Review this retry design, identify race conditions, and propose a safe implementation plan."}]
    }],
    "generationConfig": {
      "thinkingConfig": {"thinkingLevel": "medium"},
      "maxOutputTokens": 2048
    }
  }'

cURL

curl "https://www.anyfast.ai/v1beta/models/gemini-3.8-flash:generateContent?key=YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [{
      "role": "user",
      "parts": [
        {"text": "Summarize the architecture and identify the likely bottleneck."},
        {
          "fileData": {
            "mimeType": "image/png",
            "fileUri": "https://example.com/architecture.png"
          }
        }
      ]
    }]
  }'

cURL

curl "https://www.anyfast.ai/v1beta/models/gemini-3.8-flash:generateContent?key=YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [{
      "role": "user",
      "parts": [{"text": "Extract the service name, severity, and recommended action from this incident: checkout-api is timing out and requires immediate rollback."}]
    }],
    "generationConfig": {
      "responseMimeType": "application/json",
      "responseSchema": {
        "type": "object",
        "properties": {
          "service": {"type": "string"},
          "severity": {"type": "string"},
          "action": {"type": "string"}
        },
        "required": ["service", "severity", "action"]
      }
    }
  }'

cURL

curl "https://www.anyfast.ai/v1beta/models/gemini-3.8-flash:generateContent?key=YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [{
      "role": "user",
      "parts": [{"text": "Check the deployment status for checkout-api."}]
    }],
    "tools": [{
      "functionDeclarations": [{
        "name": "get_deployment_status",
        "description": "Return the current deployment status for a service.",
        "parameters": {
          "type": "object",
          "properties": {"service": {"type": "string"}},
          "required": ["service"]
        }
      }]
    }],
    "toolConfig": {
      "functionCallingConfig": {
        "mode": "ANY",
        "allowedFunctionNames": ["get_deployment_status"]
      }
    }
  }'

cURL

curl "https://www.anyfast.ai/v1beta/models/gemini-3.8-flash:generateContent?key=YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [{
      "role": "user",
      "parts": [{"text": "Find the latest stable Gemini API model and cite the source."}]
    }],
    "tools": [{"googleSearch": {}}]
  }'

Generation controls

Parameter	Type	Description
`thinkingConfig.thinkingLevel`	string	`low`, `medium`, or `high`; defaults to `medium`
`maxOutputTokens`	integer	Maximum generated tokens, up to 65,536
`responseMimeType`	string	`text/plain`, `application/json`, or `text/x.enum`
`responseSchema`	object	Schema used to constrain structured output
`stopSequences`	string[]	Up to five sequences that stop generation

Conversation and response handling

Use user and model roles for conversation history.
Preserve complete model turns and every thoughtSignature in multi-step function workflows.
Check candidates[].finishReason before consuming the output.
Read token counts from usageMetadata, including thoughtsTokenCount for reasoning usage.
Search and Maps responses can include groundingMetadata with queries, sources, and supporting segments.
Code execution can return executableCode and codeExecutionResult parts.

API Reference

View request fields, capability examples, and response schemas for Gemini 3.8 Flash.

​Model specifications

​Choose a workflow

​Request examples

​Generation controls

​Conversation and response handling

API Reference

​Official references

Model specifications

Choose a workflow

Request examples

Generation controls

Conversation and response handling

Official references