Learn how to use the Agent Behavior Specification to describe, test, and version agent behavior.
ABS plays a role for agent behavior similar to what OpenAPI plays for HTTP APIs and AsyncAPI for event-driven systems: a shared contract that developers, QA, product owners, and tooling can all read and act on.
session: Customer checks order status
behaviors:
- actor: user
action: says
content: "Where is my order #8291?"
- actor: assistant
action: calls
target: Orders API
- actor: assistant
action: informs
content: "Your order is on the way"
evaluations:
- type: contains
value: "on the way"
Three behaviors, one evaluation. Anyone can read it — PO, dev, QA.
The documentation is split into several sections:
New to ABS? Start with the Tutorial, then read the Installation guide to set up the CLI and run your first session.
The Specification v0.1 is the normative reference. It defines document format, required and optional fields, and conformance rules. Understanding the Core Model (Session, Behavior, Actor, Action) is key to reading and writing ABS documents.
Practical guides for modeling real behaviors with Patterns, composing sessions, working with tools and MCP, using the CLI, and executing specs against real agents with the Runner.
The Manifesto explains why ABS exists. Examples provide worked, narrated sessions. The Roadmap shows what's next.
v0.1 — the conceptual core is closed. Implementations in TypeScript and Python, plus a React UI editor and this docs site. See the Roadmap for open design questions deferred to v0.2+.