Agent - Go library for building LLM-based applications

Description

This library provides an architecture for building LLM-based applications.

Specifically it wraps underlying Chat interfaces for LLMs providing an application architecture that can be useful for building agents. The focus is to provide first-class support for tools and complex workflows.

This can be thought of as a native-go approach to Python frameworks such as langchain.

Usage

s := openai.NewClient("my-api-key")
p := openaichat.New(s, "gpt-4")

ts := tools.New()

a := agent.New(p,
	agent.WithFilter(agent.LimitMessagesFilter(5)),

	// Next add functions because they are one of the rare cases where we
	// intercept and directly handle completions.
	functions.WithTools(ts),
)

a.Add(agent.RoleSystem, "You are a helpful assistant.")
a.Add(agent.RoleUser, "Are you alive?")

// Allow a single call to the underlying provider.
r, err := a.Step(context.Background())
if err != nil {
	log.Fatalf("error from Agent: %v", err)
}

c, err := r.Content(context.Background())
if err != nil {
	log.Fatalf("error from Message: %v", err)
}

fmt.Println(c)

Design

Dialog

Agent is fundamentally a data model for a dialog. It contains a sequence of messages between entities (including system, user, assistant, and function).

When invoked, these messages are passed to a CompletionFunc which is ultimately a call to an LLM provider such as OpenAI. But through the use of Middleware can also provide significant flexibility and control.

CompletionFunc

The design for Agent is inspired by net/http. Most features are implemented as middleware around the underlying provider.

type CompletionFunc func(context.Context, []*Message, []ToolDef) (*Message, error)

All providers need to implement this signature to issue completion requests to the underlying LLM.

"Middleware" is implemented by wrapping the provider in layers, like an onion.

Provider

The provider is the interface for the underlying LLM. It is responsible for sending the available messages and functions to the LLM. The provided example providers also make use of the middleware pattern for implementing providing specific functionality.

For example, logging for the openaichat provider is configured like:

slog.SetDefault(slog.New(&slogor.Handler{
	Mutex:      new(sync.Mutex),
	Level:      slog.LevelDebug,
	TimeFormat: time.Stamp,
}))

s := openai.NewClient("my-api-key")
p := openaichat.New(s, "gpt-4",
	openaichat.WithMiddleware(openaichat.Logger(slog.Default())),
)

While the implementation itself composes like an onion:

func Logger(l *slog.Logger) MiddlewareFunc {
	return func(ctx context.Context, params openai.ChatCompletionRequest, next CreateCompletionFn) (
		openai.ChatCompletionResponse, error) {
		st := time.Now()

		resp, err := next(ctx, params)
		if err != nil {
			l.LogAttrs(ctx, slog.LevelError, "failed executing completion", slog.String("error", err.Error()))
			return resp, err
		}

		l.LogAttrs(ctx, slog.LevelDebug, "executed completion",
			slog.Duration("elapsed", time.Since(st)),
			slog.Int("prompt_tokens", resp.Usage.PromptTokens),
			slog.Int("completion_tokens", resp.Usage.CompletionTokens),
			slog.String("finish_reason", string(resp.Choices[0].FinishReason)),
		)
		return resp, err
	}
}

Features

Filters

Filters allow for breaking the 1-1 relationship between Agent messages and what is sent to the underlying provider.

LLMs have limited Context windows, so this provides helpful functionality for having greater control over the context without throwing away potentially valuable information.

A simple example of a filter might limit how many messages to send:

func LimitMessagesFilter(max int) FilterFunc {
	return func(ctx context.Context, msgs []*Message) ([]*Message, error) {
		if len(msgs) > max {
			return msgs[len(msgs)-max:], nil
		}
		return msgs, nil
	}
}

Filters are configured as options when creating the agent:

a := agent.New(c, agent.WithFilter(LimitMessagesFilter(5)))

Checks

Checks are the response side of filters: it's a convenient way to intercept responses from the provider chain.

func hasSecret(ctx context.Context, msg *agent.Message) error {
	c, _ := msg.Content(ctx)
	if strings.Contains(c, "secret") {
		return errors.New("has a secret")
	}

	return nil
}

Checks are configured as options when creating the agent:

a := agent.New(c, agent.WithCheck(hasSecret))

Tools

A core capability for building an Agent is providing tools. Tools allow the agent the perform actions autonomously.

func hello() (string, error) {
	return "Hello World", nil
}

// Empty parameters
params := jsonschema.Definition{
	Type:       "object",
	Properties: map[string]jsonschema.Definition{},
}

ts := tools.New()
ts.Add("hello", "receive a welcome message", params, hello)

a := agent.New(c, agent.WithTools(ts))

Behind the scenes, WithTools middleware will intercept tool invocations and run the provided function as an agent step.

Vision

Messages can include image data:

imgData, _ := os.ReadFile("camera.jpg")
m := agent.NewImageMessage(agent.RoleUser, "please explain", "camera.jpg", imgData)
a.AddMessage(m)

See example

Agent Set

An Agent Set allows an LLM to start a dialog with another LLM. It exposes two new tools for your primary agent to call:

• agent_start - starts an agent
• agent_stop - stops an agent

as := agentset.New()
as.Add("eyes", EyesAgentStartFunc())

ts := tools.New()
ts.AddTools(as.Tools())

a := agent.New(c, set.WithAgentSet(as))

This is an example of advanced control flow that is supported by the design of Agent. The implementation of AgentSet required no modifications to Agent core.

Message Attributes

Each message may contain a set of attributes that are not directly used by the LLM, but can provide important contextual clues for other parts of the application.

m := agent.NewContentMessage(agent.RoleUser, "content...")
m.SetAttr("summary", getSummary())

A special case of attributes with no content are Tags:

m := agent.NewContentMessage(agent.RoleUser, "content...")
m.Tag("important")

This works well with filters.

Dynamic Messages

The API for retrieving the content of a message is designed to support more than simply returning a string.

	content, err := m.Content(context.Background())
	if err != nil {
		fmt.Fprintf(os.Stderr, "error getting message content: %v\n", err)
		os.Exit(1)
	}

Messages support running functions to dynamically generate content.

func generateSystem(ctx context.Context) (string, error) {
    currentDate := time.Now().Format("2006-01-02")

    content := fmt.Sprintf("System Message - Date: %s", currentDate)

    return content, nil
}

msg := agent.NewDynamicMessage(agent.RoleSystem, generateSystem)
a.AddMessage(msg)

Run patterns

Agents are designed to operate in "steps" by calling:

msg, err := a.Step(context.Background())

A step is generally a single message sent to the LLM and the response returned. Middleware such as Tools can intercept those steps and run other actions instead.

For prototypes, tools or other simple use cases, it may be helpful to run Step automatically until some end condition is detected. There are some built-in helpers to support this.

RunUntil provides some sugar for running steps until either the context is canceled or a provided function returns true.

count := 0
func runTwice(ctx context.Context) bool {
	count++
	return count == 2
}

err := agent.RunUntil(context.Background(), a, runTwice)

One common usecase is to run an Agent until the Assistant responds to the user (rather than run tools). This can be easily configured with the StopOnReply check function.

a := agent.New(c, agent.WithCheck(agent.StopOnReply))

err := Run(context.Background(), a)

These patterns may not be appropriate for production applications where full control over the stopping of an agent is likely desired. These patterns should be adapted as needed.