Struct BeforeToolApply 

pub struct BeforeToolApply {
    pub tool_name: String,
    pub safety: SafetyClass,
    pub args: Value,
    pub result: Option<SyntheticToolResult>,
}

Entry point for call-type transformations, invoked before each ToolApply.

Two orthogonal intervention axes:

• Modify args (data axis): rewrite the parameters passed to the tool.
• Fill result (short-circuit): Some = skip the actual tool invocation and use this synthetic output as the result; the turn continues. This is fundamentally different from Break (which ends the entire turn) — do not confuse “intercepting a single tool” with “ending the turn”.

Fields

tool_name: String

safety: SafetyClass

The tool’s safety level, placed in the envelope for the matcher’s safety filtering.

args: Value

Modifiable tool arguments.

result: Option<SyntheticToolResult>

The result that will be produced. None = actually run the tool; Some = short-circuit.

Trait Implementations

impl Clone for BeforeToolApply

fn clone(&self) -> BeforeToolApply

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for BeforeToolApply

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

Formats the value using the given formatter.

impl HookStep for BeforeToolApply

fn event_name(&self) -> &'static str

Event name (snake_case). Used in envelope headers and matchers.

fn to_envelope(&self) -> Value

Projects the step into an input envelope — fed to command stdin / prompt templates. Contains a common header plus step-specific fields.

fn apply_verdict( &mut self, verdict: &Value, ) -> Result<HookControl, VerdictError>

Apply the handler’s output verdict (JSON) back to this step: parse the common control / additional_context fields, then handle the step-specific “fill output” fields. Returns a control directive.