Using the Agent Class

Using the Agent Class

Overview

The Agent class uses an internal AI SDK ToolLoopAgent through composition with Output prompt files and the skills system. It does not inherit from ToolLoopAgent. Use it when you need multi-step tool execution, conversation history, or a reusable agent instance. For single-shot LLM calls without tools, generateText is simpler.

When to Use This Skill

• Building multi-step agents that call tools in a loop
• Using skills (lazy-loaded instructions) with an agent
• Creating agents with structured output via aiSdk.Output.object()
• Implementing stateful conversations with messageStore
• Streaming Agent progress with onChunk
• Deciding between Agent and generateText

Import Pattern

import { Agent, aiSdk } from '@outputai/llm';
import type { MessageStore } from '@outputai/llm';
import { z } from '@outputai/core';

Agent comes from @outputai/llm. Use aiSdk.Output for structured output. Import z from @outputai/core (never from zod directly). MessageStore is the type for a pluggable getMessages / addMessages store; implement it yourself.

Construction

The prompt file is loaded and rendered at construction time. Variables and tools are fixed at construction. Skills and maxSteps come from the prompt file. The agent is ready to call generate(), generateWithStreaming(), or stream() immediately.

const agent = new Agent( {
  prompt: 'writing_assistant@v1',
  variables: {
    content_type: input.contentType,
    focus: input.focus,
    content: input.content
  },
  output: aiSdk.Output.object( { schema: reviewSchema } )
} );