> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/firebase/genkit/llms.txt
> Use this file to discover all available pages before exploring further.

# AI Package

> AI package API reference (Go)

The `ai` package provides core AI functionality including generation, models, tools, and prompts.

## Generate Options

### WithModelName()

Specifies the model by name.

```go theme={null}
ai.WithModelName("googleai/gemini-2.0-flash")
```

### WithModel()

Specifies the model instance.

```go theme={null}
model := genkit.LookupModel(g, "googleai/gemini-2.0-flash")
ai.WithModel(model)
```

### WithPrompt()

Sets the user prompt.

```go theme={null}
ai.WithPrompt("Tell me a joke about programming.")
```

### WithSystem()

Sets system instructions.

```go theme={null}
ai.WithSystem("You are a helpful coding assistant.")
```

### WithMessages()

Provides conversation history.

```go theme={null}
ai.WithMessages([]*ai.Message{
    {Role: ai.RoleUser, Content: []*ai.Part{ai.NewTextPart("Hello")}},
    {Role: ai.RoleModel, Content: []*ai.Part{ai.NewTextPart("Hi!")}},
})
```

### WithTools()

Enables tools for the model.

```go theme={null}
ai.WithTools(weatherTool, calculatorTool)
```

### WithToolChoice()

Controls tool usage.

```go theme={null}
ai.WithToolChoice(ai.ToolChoiceRequired) // Force tool use
ai.WithToolChoice(ai.ToolChoiceNone)     // Disable tools
ai.WithToolChoice(ai.ToolChoiceAuto)     // Let model decide
```

### WithConfig()

Sets generation parameters.

```go theme={null}
ai.WithConfig(&ai.GenerationCommonConfig{
    Temperature: 0.7,
    MaxOutputTokens: 1000,
    TopP: 0.9,
})
```

### WithOutputType()

Sets structured output schema from type.

```go theme={null}
type Person struct {
    Name string `json:"name"`
    Age  int    `json:"age"`
}

ai.WithOutputType(Person{})
```

### WithOutputSchema()

Sets output JSON schema.

```go theme={null}
ai.WithOutputSchema(map[string]any{
    "type": "object",
    "properties": map[string]any{
        "name": map[string]any{"type": "string"},
    },
})
```

### WithDocs()

Provides context documents.

```go theme={null}
ai.WithDocs([]*ai.Document{
    ai.Document.FromText("Context document 1"),
    ai.Document.FromText("Context document 2"),
})
```

### WithStreaming()

Enables streaming with callback.

```go theme={null}
ai.WithStreaming(func(ctx context.Context, chunk *ai.ModelResponseChunk) error {
    fmt.Print(chunk.Text())
    return nil
})
```

## Types

### Message

```go theme={null}
type Message struct {
    Role     Role
    Content  []*Part
    Metadata map[string]any
}
```

**Roles:**

* `ai.RoleUser`
* `ai.RoleModel`
* `ai.RoleSystem`
* `ai.RoleTool`

### Part

```go theme={null}
// Create parts
ai.NewTextPart("Hello")
ai.NewMediaPart("image/png", imageData)
ai.NewToolRequestPart(name, input)
ai.NewToolResponsePart(name, output)
```

### ModelResponse

```go theme={null}
type ModelResponse struct {
    Message      *Message
    FinishReason FinishReason
    Usage        *GenerationUsage
    Request      *ModelRequest
    Custom       map[string]any
}

// Methods
resp.Text() string
resp.Output(v any) error
```

### ModelRequest

```go theme={null}
type ModelRequest struct {
    Messages []*Message
    Tools    []*ToolDefinition
    Config   any
    Output   *OutputConfig
}
```

### GenerationCommonConfig

```go theme={null}
type GenerationCommonConfig struct {
    Temperature     float64
    MaxOutputTokens int
    TopK            int
    TopP            float64
    StopSequences   []string
}
```