Produce STRICT JSON with the schema: {"specs": [{"spec": string, "category": string, "difficulty": string}]}.
Generate {{num}} diverse specs.
Guidelines:
- Avoid trivial or overly broad tasks; each spec should be testable with clear inputs/outputs.
- Keep each spec concise (a few sentences) but include a few concrete input/output examples.
- Assign each spec a descriptive category (snake_case, your choice).
- difficulty ∈ {easy, medium, hard}.
Return ONLY JSON.