Function render_reference_hint_with 

pub fn render_reference_hint_with(
    tool_call_id: &str,
    verbosity: HintVerbosity,
    source_tool: Option<ToolKind>,
) -> String

Render a reference hint at the requested verbosity.

Forms (measured with cl100k_base):

Terse     > [ref: tc_42]                               ~8 tok
Standard  > [ref: tc_42, byte-identical]               ~11 tok
Verbose   > [ref: tc_42, byte-identical, from: Read]   ~15 tok

source_tool, when provided, is included only in the Verbose form — earlier verbosities intentionally drop it to stay terse.