Struct FnTool 

pub struct FnTool { /* private fields */ }

A tool built entirely from closures and configuration, implementing AgentTool without requiring a custom struct.

Use the builder methods to configure the tool’s schema, approval requirements, and execution logic.

Implementations

impl FnTool

pub fn new( name: impl Into<String>, label: impl Into<String>, description: impl Into<String>, ) -> Self

Create a new FnTool with the given name, label, and description.

The default schema accepts any object and the default execute returns an error indicating the tool is not implemented.

pub fn with_schema_for<T: JsonSchema>(self) -> Self

Set the parameters schema from a type implementing JsonSchema.

pub fn with_schema(self, schema: Value) -> Self

Set the parameters schema from a raw JSON value.

pub const fn with_requires_approval(self, requires: bool) -> Self

Set whether this tool requires user approval before execution.

pub fn with_execute<F, Fut>(self, f: F) -> Self

where F: Fn(String, Value, CancellationToken, Option<Box<dyn Fn(AgentToolResult) + Send + Sync>>) -> Fut + Send + Sync + 'static, Fut: Future<Output = AgentToolResult> + Send + 'static,

Set the execution function using the full signature.

The closure receives (tool_call_id, params, cancellation_token, on_update).

pub fn with_execute_simple<F, Fut>(self, f: F) -> Self

where F: Fn(Value, CancellationToken) -> Fut + Send + Sync + 'static, Fut: Future<Output = AgentToolResult> + Send + 'static,

Set the execution function using a simplified signature.

The closure receives only (params, cancellation_token), ignoring the tool call ID and update callback.

pub fn with_execute_async<F, Fut>(self, f: F) -> Self

where F: Fn(Value, CancellationToken) -> Fut + Send + Sync + 'static, Fut: Future<Output = AgentToolResult> + Send + 'static,

Set the execution function using an explicit untyped async signature.

This is equivalent to Self::with_execute_simple and exists as a discoverability alias for callers looking for an untyped async builder.

pub fn with_execute_typed<T, F, Fut>(self, f: F) -> Self

where T: DeserializeOwned + JsonSchema + Send + 'static, F: Fn(T, CancellationToken) -> Fut + Send + Sync + 'static, Fut: Future<Output = AgentToolResult> + Send + 'static,

Set the execution function using a typed parameter struct.

This derives the schema from T and deserializes validated params into T before calling the closure. On deserialization failure, execution returns AgentToolResult::error("invalid parameters: ...").

pub fn with_approval_context<F>(self, f: F) -> Self

where F: Fn(&Value) -> Option<Value> + Send + Sync + 'static,

Set a closure that provides rich context for the approval UI.

When the tool requires approval, this closure is called to produce context that is attached to the ToolApprovalRequest.

Trait Implementations

impl AgentTool for FnTool

fn name(&self) -> &str

Unique routing key used to dispatch tool calls.

fn label(&self) -> &str

Human-readable display name for logging and UI.

fn description(&self) -> &str

Natural-language description included in the LLM prompt.

fn parameters_schema(&self) -> &Value

JSON Schema describing the tool’s input shape, used for validation.

fn requires_approval(&self) -> bool

Whether this tool requires user approval before execution. Default is false — tools execute immediately.

fn approval_context(&self, params: &Value) -> Option<Value>

Optional rich context for the approval UI.

fn execute( &self, tool_call_id: &str, params: Value, cancellation_token: CancellationToken, on_update: Option<Box<dyn Fn(AgentToolResult) + Send + Sync>>, _state: Arc<RwLock<SessionState>>, _credential: Option<ResolvedCredential>, ) -> ToolFuture<'_>

Execute the tool with validated parameters.

fn metadata(&self) -> Option<ToolMetadata>

Optional organizational metadata (namespace, version).

fn auth_config(&self) -> Option<AuthConfig>

Optional authentication configuration for this tool.

impl Debug for FnTool

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

Formats the value using the given formatter.