AI News · Tools

Ponytail or /simplify:
prevent or clean up.

September 13, 2026 · approx. 11 min read

Both tools advertise leaner code. But they intervene at different points in the workflow. Ponytail is a skill that asks, right while the code is being written, whether it's even needed at all. /simplify is a Claude Code command that comes afterward and cleans up the finished diff. I built the same task for PlantWiz three times to see what that actually means in practice.

The mix-up is understandable, because both tools use the same word: "simplify." Ponytail is a short checklist an agent runs through before writing: does this already exist? Does a standard function cover it? Is it even needed? /simplify, on the other hand, is a review command that looks at the resulting diff after writing and searches for reuse, redundancy, and unnecessary complexity. One question comes before building, one after, and despite sharing the same goal, they lead to very different results.

That number alone is misleading. In my measurement, /simplify did solid work, just at a different point than Ponytail, as the next section shows.

The test task

A ticket, as terse as everyday tickets usually are: "Sorting for the plant list: users should be able to sort the plants in their garden by name, planting date, or location." Deliberately an open task with no technical spec, so both tools would have something to do. PlantWiz had no code for this yet, but there was already an existing sorting pattern in the same file (Sidebar.vue, which lists a garden's plants grouped by bed) and an existing test for it.

Ponytail: the question comes before the code

On the sorting task, Ponytail landed on rung 4 ("a native platform feature is enough") combined with rung 2 ("does this already exist in the repository"): a native <select> instead of a dropdown library, and the comparator for sorting was aligned with the file's existing Array.sort pattern instead of being reinvented. Result: 42 lines instead of 173, no new store, no new component, no new dependency.

The baseline variant without the checklist, by contrast, had additionally built a complete second, parallel view: a flat list across all of the garden's plants for the new sort modes, with its own markup, its own CSS classes, and its own test. Functionally correct, just more than the ticket called for, and this exact build is what the Ponytail checklist prevented, by keeping the existing grouped layout and only changing the sort order within the groups.

The test that was skipped for the parallel view is not a benefit in itself. The sort feature has three new, externally visible cases; they still need tests. In this case I would extend the existing test to cover name, planting date, and location, rather than cutting test effort across the board.

/simplify: the question comes after the code

Measured again: same diff, one pass afterward

To compare the two tools fairly, I did not take two independent implementations, but the same starting diff: the 173-line baseline variant without Ponytail, applied in a second worktree and worked on there with /simplify.

/simplify found four real issues:

• Duplicate sort logic: two nearly identical .sort() branches with the same fallback could be merged into one comparator.
• Linear search per row: mapping bed to name ran through Array.find for every rendered plant instead of a prepared map.
• Duplicate CSS: a new row class carried over rules from an already existing class almost unchanged.
• The biggest finding, but not applied: the new list was a complete second render path with duplicated markup instead of a shared component with optional columns. The skill named this but deliberately did not apply it, reasoning that it was a structural rework outside the scope of a pure simplify pass.

Three fixes were applied, and the line count barely dropped. That's how /simplify works: it makes existing code better solved, without asking whether that code should have been built at all. It noticeably does not ask that exact question at the skipped altitude finding. A review command that unilaterally cut feature scope would be the bigger risk on a real pull request, so the restraint there makes sense.

The cost: a real review pass instead of a text snippet

Ponytail's cost is predictable: a fixed number of tokens on every call. /simplify costs differently: it triggers a full, multi-part review of the diff, in my run across four separate categories. That's not a fixed text block in context, but its own work step with its own token usage, roughly on the order of a full additional pass over the same task. In return, that cost only occurs when deliberately triggered, not automatically on every coding task.

Direct comparison

Which tool, when

The two tools don't compete, they answer different questions. Ponytail saves the most where an agent would otherwise build too much. /simplify improves what has already been built, but doesn't change whether it should have been built. A team using both gets less unnecessary code and cleaner necessary code, but neither tool replaces the question that should stand at the start of a ticket: what is actually needed here.