---
title: 'A plain greeter'
description: 'The smallest agent worth running: one model, one prompt from the catalogue, and no tools at all.'
position: 1
---

# A plain greeter

> The smallest useful agent is a name and a model, with no tools attached. That
> makes the prompt the whole contract: it is the only thing deciding how the
> agent answers, and it lives in the catalogue rather than in the file. This one
> welcomes a person by name and stops at two sentences.

The whole agent is a single `deep-agents/greeter/index.ts` file. Drop it into a
workspace laid out the way
[Getting started with agents](/docs/sdk/agents/building-agents) describes, then
run it with `stackbone dev`.

```ts
// deep-agents/greeter/index.ts
import { defineDeepAgent } from '@stackbone/sdk/deep';

export default defineDeepAgent({
  name: 'greeter',
  model: 'openai/gpt-4o-mini',
});
```

The voice lives in the [prompt catalogue](/docs/sdk/platform/prompts), not in
the file. In Studio, open this agent and write the prompt keyed `greeter`, then
publish it:

```text
You are a warm, concise greeter.
Welcome the person by name when they give it, and offer one helpful next step.
Keep every reply to two sentences.
```

Run `stackbone dev`, then:

```sh
curl http://127.0.0.1:4242/openai/v1/chat/completions \
  -H 'content-type: application/json' \
  -H 'authorization: Bearer local-dev' \
  -d '{"model":"greeter","messages":[{"role":"user","content":"Hi, I am Sam"}]}'
```

You pick the agent with the request's `model` field, which matches the folder
name. `greeter` reaches this file.

## What's next

- **[A config-driven agent](/docs/examples/agents/config-driven)**: move the
  tone out of the prompt so an operator can change it without republishing it.
- **[A retrieval-backed support agent](/docs/examples/agents/retrieval-backed)**:
  give the agent tools that search a knowledge base and read a database.
- **[What is an agent](/docs/sdk/agents/overview)**: the model behind this
  example.