Struct SpawnAgentTool 

pub struct SpawnAgentTool { /* private fields */ }

Internal tool for spawning sub-agents

This tool is automatically added to agents that have depth_limit > current_depth. It allows recursive task decomposition with safety limits.

Implements rig::tool::ToolDyn for integration with RigAgentLoop.

Implementations

impl SpawnAgentTool

pub fn new( current_depth: u32, max_depth: u32, parent_task_id: Arc<str>, event_log: EventLog, ) -> Self

Create a new SpawnAgentTool (minimal - for testing without MCP)

Arguments

• current_depth - Current recursion depth (starts at 1 for root)
• max_depth - Maximum allowed depth (default 3)
• parent_task_id - ID of the parent task
• event_log - Shared event log for observability

pub fn with_mcp( current_depth: u32, max_depth: u32, parent_task_id: Arc<str>, event_log: EventLog, mcp_clients: FxHashMap<String, Arc<McpClient>>, mcp_names: Vec<String>, cancel_token: CancellationToken, ) -> Self

Create a new SpawnAgentTool with MCP clients (for production use)

Arguments

• current_depth - Current recursion depth (starts at 1 for root)
• max_depth - Maximum allowed depth (default 3)
• parent_task_id - ID of the parent task
• event_log - Shared event log for observability
• mcp_clients - Connected MCP clients for child agent tools
• mcp_names - MCP server names to pass to child agents
• cancel_token - Parent’s cancellation token for cooperative shutdown

pub fn with_parent_config( self, model: Option<String>, provider: Option<String>, temperature: Option<f32>, tools: Vec<String>, ) -> Self

Set parent configuration to propagate to child agents.

Without this, child agents would lose model, provider, temperature, and tools configuration from the parent — running with defaults.

pub fn name(&self) -> &str

Get the tool name

pub fn definition(&self) -> ToolDefinition

Get the JSON Schema definition for this tool

Note: OpenAI’s strict mode requires ALL properties in required and additionalProperties: false. We keep the schema simple with only required fields - context and max_turns use sensible defaults.

pub async fn call(&self, args: String) -> Result<String, SpawnAgentError>

Execute the spawn_agent tool

Creates and runs a child RigAgentLoop with inherited MCP clients. The child agent runs to completion and its result is returned.

Errors

Returns an error if:

• Current depth >= max depth (depth limit reached)
• Invalid arguments
• Child agent execution fails

pub fn can_spawn(&self) -> bool

Check if spawning is allowed at current depth

pub fn child_depth(&self) -> u32

Get the depth that child agents would have

Trait Implementations

impl Clone for SpawnAgentTool

fn clone(&self) -> SpawnAgentTool

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for SpawnAgentTool

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl ToolDyn for SpawnAgentTool

fn name(&self) -> String

fn definition( &self, _prompt: String, ) -> Pin<Box<dyn Future<Output = ToolDefinition> + Send + '_>>

fn call( &self, args: String, ) -> Pin<Box<dyn Future<Output = Result<String, ToolError>> + Send + '_>>