Quickstart: Build an Agent in 5 Minutes

The Problem

CLAUDE.md files work for single-repo instructions, but they break down when you need:

  • Versioning – no semver, no way to pin behavior to a release
  • Testing – no way to unit-test a markdown file’s tools or memory
  • Memory – no persistent state across conversations
  • Sharing – no way to distribute agent logic as a single artifact
  • Composition – no way to wire multiple agents together through MCP

Abbyfile packages agent logic as a compiled Go binary. Claude Code remains the LLM – the binary is just a packaging format.

Prerequisites

  • Claude Code (the LLM runtime that loads and runs agents)
  • Go 1.24+ (only needed for go install or building from source)

Step 1: Install the CLI

Pick one:

# Option A: Go users
go install github.com/teabranch/abbyfile/cmd/abby@latest

# Option B: Pre-built binary
curl -sSL https://raw.githubusercontent.com/teabranch/abbyfile/main/install.sh | sh

# Option C: From source
git clone https://github.com/teabranch/abbyfile.git
cd abbyfile
make build    # → build/abby

Step 2: Create an Abbyfile

Create an Abbyfile (or abbyfile.yaml) at your project root:

version: "1"
agents:
  my-agent:
    path: agents/my-agent.md
    version: 0.1.0

This declares one agent named my-agent, pointing to its .md file.

Step 3: Write the Agent Definition

Create agents/my-agent.md with dual frontmatter (two --- blocks) followed by the system prompt:

---
name: my-agent
memory: project
---

---
description: "A helpful assistant"
tools: Read, Bash
---

You are a helpful assistant. You answer questions clearly and concisely.
When you have tools available, use them to gather information before responding.

Block 1 sets identity: name and memory (any value enables it). Block 2 sets capabilities: tools (comma-separated) and description. Body is the system prompt baked into the binary.

See the Abbyfile Format Guide for full details.

Step 4: Build 

./build/abby build
# Building my-agent...
#   → ./build/my-agent
# Updated .mcp.json (claude-code)

# Target a specific runtime or all runtimes
./build/abby build --runtime codex    # → .codex/config.toml
./build/abby build --runtime all      # → all detected runtimes

# Optional: also generate a Claude Code plugin directory (with skills support)
./build/abby build --plugin
# → ./build/my-agent.claude-plugin/

Step 5: Explore 

# Version (semver, machine-parseable)
./build/my-agent --version
# my-agent v0.1.0

# JSON manifest (tools, memory, version)
./build/my-agent --describe

# System prompt
./build/my-agent --custom-instructions

# Run a tool directly
./build/my-agent run-tool read_file --input '{"path":"/etc/hostname"}'

# Memory operations
./build/my-agent memory write notes "Remember this for later"
./build/my-agent memory read notes
./build/my-agent memory list
./build/my-agent memory delete notes

# Validate wiring (checks prompt, tools, memory, version)
./build/my-agent validate

# Runtime config overrides (no rebuild needed)
./build/my-agent config get                    # show compiled defaults
./build/my-agent config set model opus         # override the model hint
./build/my-agent config reset model            # revert to default

Step 6: Connect to Your Runtime

abby build auto-generates MCP config for detected runtimes. For Claude Code, this is .mcp.json:

{
  "mcpServers": {
    "my-agent": {
      "command": "/path/to/build/my-agent",
      "args": ["serve-mcp"]
    }
  }
}

Or install the binary explicitly:

./build/abby install my-agent                  # local install, auto-detect runtimes
./build/abby install -g my-agent               # global install
./build/abby install --runtime codex my-agent  # target Codex specifically

Supported runtimes:

Runtime Local Config Global Config
Claude Code .mcp.json ~/.claude/mcp.json
Codex .codex/config.toml ~/.codex/config.toml
Gemini CLI .gemini/settings.json ~/.gemini/settings.json

Your runtime auto-discovers the agent via MCP. It sees the agent’s tools, can read its system prompt, and can interact with its memory.

What You Get vs. a CLAUDE.md

Capability CLAUDE.md Abbyfile Binary
System prompt Markdown file in repo Baked into binary, override for dev
Versioning Git history only Semantic versioning (--version)
Tools Described in prose Registered, validated, executable
Memory None Persistent KV store per agent
Testing Manual go test, integration tests, validate
Sharing Copy the file Binary distribution
Discovery Claude reads the file MCP auto-discovery via serve-mcp
Machine-readable No --describe returns JSON manifest

Next Steps

Abbyfile is an open-source project licensed under MIT.

This site uses Just the Docs, a documentation theme for Jekyll.