Function render_system 

pub fn render_system(
    template: &str,
    workspace: &Path,
    skills: &[Skill],
    tools: &[ToolSpec],
) -> Result<String, Error>

Renders a SYSTEM.md template: {{ workspace }} becomes the workspace path, skills holds the discovered skills as name, description, and path fields, and tools holds the advertised tool specs as name, description, and parameters (the JSON schema, renderable with tojson) — all there for {% for %}/{% if %}. Undefined variables render empty; syntax and filter errors return with template positions.

The optional sections (render_system_with_sections) are absent here: a template that references them renders those parts empty, exactly as a caller that passes None for each.