How to Build a Simple AI Agent

export const tools = [
  {
    name: "search_docs",
    description: "Search internal documentation for a given query and return matching snippets",
    input_schema: {
      type: "object",
      properties: {
        query: { type: "string", description: "The search query" },
      },
      required: ["query"],
    },
  },
  {
    name: "create_ticket",
    description: "Create a support ticket. Only call this after confirming the details with the user.",
    input_schema: {
      type: "object",
      properties: {
        title: { type: "string" },
        description: { type: "string" },
        priority: { type: "string", enum: ["low", "medium", "high"] },
      },
      required: ["title", "description", "priority"],
    },
  },
]

You are a support assistant. You can search internal documentation and
create support tickets.

Rules:
- Always search the docs before answering a question you're not certain about
- Never create a ticket without first summarizing the details back to the
  user and getting explicit confirmation
- If you're not confident in an answer, say so instead of guessing
- Keep responses under 150 words unless the user asks for more detail

import Anthropic from "@anthropic-ai/sdk"
import { tools } from "./tools"
import { executeTool } from "./execute-tool"

const client = new Anthropic()
const MAX_STEPS = 8

export async function runAgent(userTask: string) {
  const messages: Anthropic.MessageParam[] = [{ role: "user", content: userTask }]

  for (let step = 0; step < MAX_STEPS; step++) {
    const response = await client.messages.create({
      model: "claude-sonnet-4-5",
      max_tokens: 1024,
      system: SYSTEM_PROMPT,
      tools,
      messages,
    })

    const toolUse = response.content.find((block) => block.type === "tool_use")
    messages.push({ role: "assistant", content: response.content })

    if (!toolUse) {
      return response.content // agent is done, no more tools requested
    }

    const result = await executeTool(toolUse.name, toolUse.input)
    messages.push({
      role: "user",
      content: [{ type: "tool_result", tool_use_id: toolUse.id, content: result }],
    })
  }

  throw new Error("Agent exceeded max steps without finishing")
}

export async function executeTool(name: string, input: Record<string, unknown>) {
  switch (name) {
    case "search_docs":
      return searchDocs(input.query as string)

    case "create_ticket":
      // A real safeguard: this still requires a human-reviewed confirmation
      // step in the product UI before the ticket is actually created.
      return queueTicketForConfirmation(input)

    default:
      return { error: `Unknown tool: ${name}` }
  }
}