output-dev-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 } )
} );

Constructor Options

Option	Type	Default	Description
prompt	string	(required)	Prompt file name (e.g. 'writing_assistant@v1')
promptDir	string	-	Override the stack-resolved prompt directory
variables	PromptVariables	-	Template variables rendered at construction
tools	AI SDK tools	-	Caller tools; merged with prompt YAML tools (load_skill last)
stopWhen	function or function[]	-	Custom stop condition (overrides prompt maxSteps when tools exist)
output	aiSdk.Output	-	Structured output spec (e.g. aiSdk.Output.object({ schema }))
messageStore	MessageStore	-	Pluggable store for multi-turn history