Claude skills for Brand Voice, tested
Skills for brand voice work, measured on voice tasks. Each was the same task, run twice, once with the skill loaded and once without it, and what is below is what changed. Ranked by how many models the rule found a clear effect on, never by the size of one.
Measured on 3 models (Claude, GPT & Gemini): Claude Haiku 4.5, GPT-5 mini, Gemini 3.1 Flash Lite.
The model is given a brand brief and asked for a short piece of copy. There is no answer key; a grader sees the with and without outputs, blind and in random order, and picks one. The score is how often the skill's output was preferred.
What helped, and on how many models
First
skills/brand-voice affaan-m/ECC
Voice
Helped clearly on Claude Haiku 4.5, Gemini 3.1 Flash Lite and GPT-5 mini. Measured against no skill loaded.
A judge preferred its output 24 times in 30 over the no-skill version. Instruction arm: not applicable to a blind preference.
- Claude Haiku 4.5 · helped
- Gemini 3.1 Flash Lite · helped
- GPT-5 mini · helped
Cost per task, with the skill loaded: about $0.00101. Adds about 1,200 tokens of context to every request.
Second
skills/brand-voice rampstackco/claude-skills*
Voice
Helped on Gemini 3.1 Flash Lite; no reliable difference on Claude Haiku 4.5 and GPT-5 mini. Measured against no skill loaded.
A judge preferred its output 21 times in 30 over the no-skill version. Instruction arm: not applicable to a blind preference.
- Claude Haiku 4.5 · unclear
- Gemini 3.1 Flash Lite · helped
- GPT-5 mini · unclear
Cost per task, with the skill loaded: about $0.00334. Adds about 5,700 tokens of context to every request.
The numbers
How to read these tables
How to read these tables
- Without -> with
- The score on the task set with no skill loaded, then with the skill loaded. For classes scored against an answer key, this is the share of seeded items found. For classes scored by blind comparison, it is how often a grader preferred the skill's output over the baseline's, with the baseline shown as the complement.
- Effect (range)
- With minus without, averaged over the models tested, with the lowest and highest per-model value in brackets. Per-model intervals are on each skill's page.
- Orbit
- Stable: delta at or above the pass threshold, and the interval excludes zero
- Past the horizon: delta at or below the failure floor, and the interval excludes zero
- In free drift: the interval spans zero, or the delta sits between the floor and the threshold
- Unobservable: the cell cannot be classified: sub-case (a) an unbounded scale, or sub-case (b) both arms at the same bound
A fifth value, Decaying, is defined and appears once a skill has been re-tested: a cell previously Stable that has fallen below the pass threshold on a later run.
- Cohort
- The repository that publishes the skill. Rows marked with an asterisk come from the repository the operator of this site maintains, so those are the operator measuring its own work. The rest were chosen by a stated rule and not by preference.
- Commit
- The exact version tested. Later commits are not covered by this verdict.
- Injected context tokens
- How much text the skill adds to the model's context. This is cost, not quality; a bigger number is not a better one. Measured from the input tokens the API reported on the with arm, averaged over that skill's records.
- Tested
- The date. Verdicts age as models change.
Voice
| Skill | Cohort | Without -> with | Effect (range) | Orbit | Injected context tokens | Tested |
|---|---|---|---|---|---|---|
| No skill loaded | baseline | 25% | 0 by definition | 0 | 2026-08-30 | |
| One-line instruction instead | baseline | instruction arm: not applicable to a blind preference | 0 by definition | 0 | 2026-08-30 | |
skills/brand-voice from affaan-m/ECC d8409a4b0813 Best result in this test | affaan-m/ECC | 20% -> 80% baseline shown as the complement | +0.60 [+0.60, +0.60] | Stable | 1,170 | 2026-08-30 |
skills/brand-voice from rampstackco/claude-skills 047924252254 | rampstackco/claude-skills* | 30% -> 70% baseline shown as the complement | +0.40 [+0.20, +0.60] | In free drift on 2 of 3 | 5,674 | 2026-08-30 |
| Averaged over three models; per-model results on each skill's page. Ranked within this class only. | ||||||
Ranked within this topic by how many models the rule found a clear effect on, which is a count of verdicts and never the size of one. Two classes are two answer keys on two scales, so no effect here is compared with another. Every class, with its full table.