Hello World

Create a file called hello.keel:

use std/io
use std/schedule

agent Hello {
  @tools [io]
  @role "A friendly greeter"

  @on_start {
    schedule.every(5.seconds, () => {
      io.notify("Hello from Keel!")
    })
  }
}

run(Hello)

Run it:

KEEL_OLLAMA_MODEL=gemma4 keel run hello.keel

Output:

⚡ LLM provider: Ollama (http://localhost:11434)
▸ Starting agent Hello
  role: A friendly greeter
  model: gemma4 (ollama @ http://localhost:11434)

  ⏱ schedule.every(5.seconds)
  ▸ Hello from Keel!

  ▸ Agent running. Press Ctrl+C to stop.
  ▸ Hello from Keel!
  ▸ Hello from Keel!

Press Ctrl+C to stop.

What just happened?

1. use std/io, use std/schedule — imports the stdlib modules this file uses. Each import binds a lowercase module name (io, schedule).
2. agent Hello — declares an agent.
3. @tools [io] — grants the agent access to the effectful io module. Capabilities are deny-by-default inside agents.
4. @role "..." — an attribute describing what the agent does. Bound to the LLM provider for any ai.* calls.
5. @on_start { ... } — a lifecycle hook that runs when the agent starts.
6. schedule.every(5.seconds, () => { ... }) — schedules a recurring block. schedule is a stdlib module, not a keyword.
7. io.notify(...) — prints to the terminal.
8. run(Hello) — starts the agent. run is a built-in free function — no import needed.

Two imports declare everything this program touches — see The Standard Library.

Using AI

use std/ai
use std/io
use std/schedule

type Mood = happy | neutral | sad

task analyze(text: str) -> Mood {
  ai.classify(text, as: Mood) ?? Mood.neutral
}

agent MoodBot {
  @tools [io]
  @role "Analyzes the mood of text"

  @on_start {
    schedule.every(10.seconds, () => {
      mood = analyze("I love building programming languages!")
      io.notify("Mood: {mood}")
    })
  }
}

run(MoodBot)

ai.classify sends the text to the LLM and parses the response into one of the enum variants. ?? supplies a default when the LLM is unavailable or the response doesn’t match.

Next: Your First Agent →