tool-result-traps

# Tool Result Traps Promoted from the always-loaded `~/.claude/rules/tool-use-patterns.md` rule, whose stub points here. The section bodies below are that rule's verbatim text. One law across all of them: **an empty result, a green exit, and a well-formed line of output are each claims about *mechanics*, not about *content*.** Every trap here produces output that is indistinguishable from a correct answer — no error, no warning, nothing on stderr — and the damage lands when that output is used as a verdict: "no duplicate exists", "the rename is complete", "nothing was lost", "the agent got its input". In one case the diagnostic *was* written — and the caller's own `2>/dev/null` is what made it disappear. The recurring fix is equally uniform: **control-test any negative that gates an action.** Re-run the same command shape against something you *know* is present. If the control also comes back empty, the tool is broken, not the tree clean. One control run is cheap; a wrong negative is a confidently-reported non-finding. ## When to Use This Skill | Use this skill when... | Skip when... | |---|---| | A zero-match or empty result is about to be reported as "clean", "complete", or "none found" | The result is non-empty and you are acting on what it contains | | Deduping before filing an issue, or concluding nobody reported something | Reading a single known file whose path you just listed | | Declaring a bulk rename, migration, or sweep finished | Mid-sweep, still transformin...