Agents

An agent is a named execution profile that binds a model name and a list of tools. Agents don't do anything on their own — they are referenced in pipeline run statements or selected implicitly by workflow stage/review steps to declare which model and tools should handle a task.

Syntax

agent <name> {
  [ model: "<model-name>" ]
  , tools: [tool_a, tool_b]
}

The model field is optional. When omitted, the agent uses the runtime default.

Example

tool web_search(query: String) -> List[Obj{title: String, url: String, snippet: String}] {}

agent planner {
  model: "gpt-4.1"
  , tools: [web_search]
}

-- model omitted — uses the selected adapter's default
agent writer {
  tools: []
}

Rules

model is optional. When omitted, the runtime uses the selected adapter's default model or the mock handler. AGL_OPENAI_MODEL and AGL_ANTHROPIC_MODEL provide deployment-wide overrides (see Model mapping).
tools is required. Use [] for an empty tool list.
Tool names are identifiers and must be declared with tool definitions in the DSL.
Agent names must be unique within a file.
Duplicate tool names in the list are a parse error.

Using an agent

Reference an agent in a pipeline run statement with by:

let r = run research with { topic: topic } by planner;

When by is omitted for a standard task handled by a live adapter, the runtime uses that adapter's configured default model. Tasks declared by agent require an explicit agent binding.

In workflows, the agent is attached directly to the step:

stage plan = planner does draft_outline(topic);

Model resolution

Situation	Model used
`by agent_name` present, `model` declared	`agent_name.model` from the DSL (mapped in anthropic mode)
`by agent_name` present, `model` omitted	Provider default or `AGL_OPENAI_MODEL` / `AGL_ANTHROPIC_MODEL` override
`by` omitted, live provider mode	Provider default or deployment override
`by` omitted, mock mode	no model needed

Tools

Tools are identifiers that activate additional adapter behavior in live and anthropic mode.

Currently supported tools:

Tool	Effect in live/anthropic mode
`web_search`	Exposes a typed search tool that model tasks may call at runtime
`fetch_url`	Fetches page content and exposes extracted text to model tasks

In mock mode, tools are parsed and stored but do not trigger external network calls.

AgentLang