A technical spec has one job: let reviewers find the flaw before the code does. Most specs fail this job because they describe the happy path in detail and gesture vaguely at 'error handling' — reviewers can't find what isn't written. This skill writes specs that make the hard parts explicit: the data model and why it's shaped this way rather than another, the state machine for anything with multiple states, the failure modes and what the system does in each, the security surface and how it's protected, the performance assumptions and what breaks them, and the open questions that could invalidate the design. It follows the structure reviewers expect so they can get to the substance faster. Describe your feature and technical context; get back a spec your team can review, not just approve.