Build your first agent

In this guide you will install the compiler, scaffold a project, build it, and run your agent for the first time. By the end you will have a working binary that answers a question. It should take about ten minutes.

Prerequisites

You need two things before you start:

• The Rust toolchain, installed with rustup. The default standalone archetype compiles your agent with cargo, so Rust must be available on your build machine. Install it at rustup.rs.
• An Anthropic API key. The scaffolded agent uses Anthropic as its model provider.

Install agentc

Run the installer script. It places the agentc binary in the directory you pass with --install-dir.

curl -sSfL https://install.agentc.sh | bash -s -- --install-dir ~/.local/bin

Verify the installation:

agentc --version

Scaffold a project

Create a new project with agentc init:

agentc init my-agent
cd my-agent

You should see:

 ✓ Created my-agent

This creates a ready-to-build project. The important file is agent.acl, the manifest. Open it to see what was generated:

build {
  archetype = "standalone"
}

providers {
  anthropic {
    models = ["claude-haiku-4-5"]
    config {
      api_key = secret(runtime("ANTHROPIC_API_KEY"))
    }
  }
}

agent "my-agent" {
  graph {
    type = "react"
  }

  version     = "0.1.0"
  description = "A helpful assistant."
  prompt      = "You are a helpful assistant."

  model {
    provider = "anthropic"
    name     = "claude-haiku-4-5"
  }
}

http_server {
  host = runtime("HTTP_HOST", "127.0.0.1")
  port = runtime("HTTP_PORT", 8080)

  protocol {
    ag_ui {}
  }
}

This manifest defines a minimal agent with no tools. It uses the standalone archetype, runs on the ReAct graph, connects to Anthropic, and defines an HTTP server with the AG-UI protocol for later. The runtime() values, including the API key, are read from the environment when the binary starts, not baked in at build time.

Build

Compile the agent:

agentc build

The compiler processes the manifest, prepares any tools, generates a project, and compiles it. When it finishes, the binary is at artifacts/build/my-agent.

Run it

Set your API key and ask the agent a question with the binary's run command:

export ANTHROPIC_API_KEY=your_key_here
./artifacts/build/my-agent run "Hello, who are you?"

The agent calls the model and prints its answer, then exits. You have a working agent.

What you will do next

Right now the agent can only talk. In Add your first tool you will give it a tool and watch it get called during a run.