Reference: [AgentDef]

Declarative agent definition on a host object. See ../concepts/agents.md for usage.

Attribute properties

Property	Type	Notes
Name	string	Agent name. Must match ^[a-zA-Z_][a-zA-Z0-9_-]*$.
Model	string	"provider/model". May be left unset and assigned after resolution.
Instructions	string	Static system prompt.
Tools	string[]	["*"] = all [Tool] methods on the host, [] = none, or explicit tool names.
Guardrails	string[]	Same filtering semantics as Tools.
Agents	string[]	Sub-agent names, resolved from other [AgentDef] methods on the same host.
Strategy	Strategy	Required when Agents is non-empty.
MaxTurns	int
MaxTokens	int
Temperature	double

Return types

The method's return type determines how much the attribute has to specify:

Return type	Meaning
void	Defined entirely by the attribute.
string	A no-arg method becomes InstructionsFn — dynamic instructions re-evaluated on every submit.
Agent	A full factory; the returned agent is used as-is.

Resolution

• Agent.FromInstance(object host) → List<Agent> — every [AgentDef] method.
• Agent.FromInstance(object host, string name) → Agent — a single one by name.

Sub-agent references in Agents are resolved against the same host, so a coordinator and its children can be declared side by side in one class.

Interaction with [Tool] and [Guardrail]

[Tool] and [Guardrail] methods on the host are attached automatically unless the Tools / Guardrails filters narrow them. This is why an [AgentDef] with Tools = new string[0] is meaningful — it opts out of the host's tools rather than merely leaving them unset.

Related

• api.md — Agent, AgentBuilder, Strategy
• agent-schema.md — the serialized wire format