The root topology block, pattern catalog, and syntax fundamentals of the .at language

Topology Declaration

Every .at file begins with a single topology declaration. This is the root of your multi-agent system — it names the topology, declares its coordination patterns, and contains all agents, flows, gates, and configuration.

Syntax

topology my-team : [pipeline, human-gate] {
  # agents, flow, gates, and other blocks go here
}

The declaration has three parts:

Part	Example	Description
Name	`my-team`	A lowercase-with-hyphens identifier
Patterns	`[pipeline, human-gate]`	One or more coordination patterns
Body	`{ ... }`	All blocks for this topology

Patterns Catalog

Patterns tell AgenTopology how your agents coordinate. You can combine multiple patterns.

Pattern	Description
`pipeline`	Agents run in a fixed sequence, each passing output to the next
`supervisor`	A lead agent delegates to and reviews work from sub-agents
`fan-out`	Work is sent to multiple agents in parallel, then merged
`orchestrator-worker`	An orchestrator dynamically assigns tasks to a pool of workers
`blackboard`	Agents read and write to a shared knowledge store
`debate`	Agents argue positions and a judge synthesizes a conclusion
`consensus`	Agents iterate toward agreement through rounds of discussion
`market-routing`	Tasks are routed to agents based on bids or capability matching
`event-driven`	Agents react to events rather than following a fixed flow
`human-gate`	A human must approve before work continues past a checkpoint

Combine patterns with commas:

topology review-team : [pipeline, human-gate, fan-out] {
  # ...
}

Syntax Basics

The .at language uses a small set of primitives across all blocks.

Comments

Lines starting with # are comments:

# This is a comment
topology demo : [pipeline] {
  # Another comment
}

Identifiers

All names use lowercase letters and hyphens:

topology my-team : [pipeline] { }
agent code-reviewer { }

Strings

Strings are double-quoted:

role: "Senior code reviewer"

Numbers and Booleans

retry: 3
isolation: true

Lists

Square brackets delimit lists:

tools: [Read, Write, Grep]
patterns: [pipeline, fan-out]

Blocks

Curly braces delimit blocks. Blocks can be nested:

agent planner {
  model: sonnet
  prompt {
    "You are a project planner."
  }
}

Tips

A file must contain exactly one topology declaration.
The topology name becomes the identifier used by CLI commands like agentopology validate my-team.at.
Pattern selection affects validation rules. For example, human-gate requires at least one gates block.

Topology Declaration

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