BF pencil-skill
Create and edit Pencil (.pen) design files programmatically. Generate UI designs as JSON-based .pen files with themes, variables, components, and layouts. Includes CLI tools for reading, searching, editing, and validating .pen files without requiring the Pencil desktop app. Requires Node.js 18+. Schema version 2.8.
As a process F 40/100 · Will not run — References files that are not bundled: assets/example-card.pen, assets/reddit-ui.pen
What is at stake
Medium-severity findings: the skill is probably honest, but read what alarmed the scanner.
Below is the worst case for this category. The finding here is medium: the guard saw a sign, not a proof.
The instructions or scripts send data out: environment variables, keys, file contents, chat history. You may never notice, because the agent performs the upload as "part of the task".
If the upload is not needed for the task, remove it: catalogs flag such skills and delist them. If it is needed, name the destination explicitly, say what leaves the machine, and give the user a switch.
How to improve
- Say in the description WHEN to use the skill ("use when…", example requests): that is the agent's main cue.
- The text references files that are not there: add them or drop the references.
- Your own cases (evals/evals.json, 4–6 real requests with expected answers): the full check would then run those instead of a model-drafted suite.
- A spec.yaml with trigger phrases and assertions — a behaviour contract for CI; `skilltest init` writes a template.
Guard findings · 1
✓ No critical or high findings
Medium and low: 1
-
medium Exfiltration
net-credential-userules/token-workflow.md:10Credential used in a network call (verify the destination is the intended service)You must register tokens before getting started with design. Workflow: ① Register tokens with `set-variables` → ② Confirm registration with `get-variables` → ③ Reference `$token.name` in design. If yo
Files scanned: 59. Evidence is masked. Grey chips explain why severity was lowered.
Against the Agent Skills spec
- warning
description-no-whendescription does not say WHEN to use the skill (no "use when") - warning
missing-refreference to a missing file: assets/example-card.pen - warning
missing-refreference to a missing file: assets/reddit-ui.pen
Process rating: all ten parameters 40/100
- 0Tools and files. 2 referenced file(s) missing: assets/example-card.pen, assets/reddit-ui.pen
- 0Result and completion. Does not say what the result is
- 0Inputs and preconditions. Does not say what the process needs to start
- 0Progress reporting. Says nothing while it works
- 20When it triggers. No condition that starts the skill
- 30Running it twice. 9 mutating operations with no state check
- 70Failures and branches. 6 branches
- 100Steps. 123 steps
- 100Consistency. Name and required fields are in place
- 100Execution cost. Instruction body is 3355 tokens
- medium Safety rules and hard prohibitions inside a skill: they belong in the system prompt, here they protect nothing
- low 18 top-level sections: this looks like several domains in one skill
Everything here is measured from the skill text rather than judged by a model, so the numbers are checkable. A parameter weighs more when it is a more common reason for the process to stall.
Quality signals
- +5Description has no quoted example phrases that should trigger the skill
- +4Description does not say when NOT to use the skill (false activations)
- +3Output format is not stated: the model decides each time
- -31 of 10 scripts are never mentioned in SKILL.md
- +1No license
- +2Single-language instructions
- +3Description length 316: enough signal without eating the budget
- +4Structure: 54 headings
- +3Step-by-step instructions: 123 items
- +4Has examples (11 code blocks)
- +4Reference files are cited in the instructions (5 of 43)
Quality base 70; lint remarks subtract, signals add up to 100. Result: 64.