LLMKit

Minimal Go library for calling LLM APIs. Unified interface for OpenAI GPT, Anthropic Claude, Google Gemini, and xAI Grok. One package, three functions, zero magic.

Feature Freeze: The API is stable. No new features will be added. Bug fixes only.

Install

go get github.com/aktagon/llmkit

Usage

provider := llmkit.Provider{
    Name:   "anthropic",
    APIKey: os.Getenv("ANTHROPIC_API_KEY"),
}

resp, err := llmkit.Prompt(ctx, provider, llmkit.Request{
    User: "Hello",
})
if err != nil {
    log.Fatal(err)
}
fmt.Println(resp.Text)
fmt.Printf("Tokens: %d in, %d out\n", resp.Tokens.Input, resp.Tokens.Output)

System Prompt

resp, err := llmkit.Prompt(ctx, provider, llmkit.Request{
    System: "You are a helpful assistant.",
    User:   "Hello",
})

Custom Model

provider := llmkit.Provider{
    Name:   "anthropic",
    APIKey: os.Getenv("ANTHROPIC_API_KEY"),
    Model:  "claude-3-opus-20240229",
}

Custom Base URL

Use any OpenAI-compatible API (LiteLLM, vLLM, Ollama, etc.):

provider := llmkit.Provider{
    Name:    "openai",
    APIKey:  os.Getenv("OPENAI_API_KEY"),
    BaseURL: "http://localhost:4000",
}

Providers

Provider	Name	Default Model	Env Var
Anthropic	anthropic	claude-sonnet-4-5	ANTHROPIC_API_KEY
OpenAI	openai	gpt-4o-2024-08-06	OPENAI_API_KEY
Google	google	gemini-2.5-flash	GEMINI_API_KEY
Grok	grok	grok-3-fast	XAI_API_KEY

Feature Matrix

Feature	Anthropic	OpenAI	Google	Grok
Prompt	Y	Y	Y	Y
Agent	Y	Y	Y	Y
Tools	Y	Y	Y	Y
Structured Output	Y	Y	Y	Y
File Upload	Y	Y	Y	Y
Image Input	Y	Y	Y	Y

Option Support Matrix

Option	Anthropic	OpenAI	Google	Grok
WithTemperature	Y	Y	Y	Y
WithTopP	Y	Y	Y	Y
WithTopK	Y	-	Y	Y
WithMaxTokens	Y (req)	Y	Y	Y
WithStopSequences	Y	Y	Y (max 5)	Grok-3
WithSeed	-	Y	Y	Y
WithFrequencyPenalty	-	Y	-	Grok-3
WithPresencePenalty	-	Y	-	Grok-3
WithThinkingBudget	Y (≥1024)	-	Gemini 2.5	-
WithReasoningEffort	-	Y (o-series)	Gemini 3	-

API

func Prompt(ctx context.Context, p Provider, req Request) (Response, error)
func NewAgent(p Provider) *Agent
func UploadFile(ctx context.Context, p Provider, path string) (File, error)

License

FSL-1.1-Apache-2.0 - Free for internal use, education, and research. Converts to Apache 2.0 after 2 years. See LICENSE.