The skill is reasonably efficient but includes some redundancy — the 'Known GTFOBins attack patterns' section partially duplicates what the workflow already covers, and the Notes section restates design constraints mentioned in the classification table. The security preamble is justified but lengthy. Overall mostly efficient with room to tighten.

Provides fully executable Go test patterns with concrete naming conventions, specific file paths (interp/builtins/<command>/builtin_<command>_pentest_test.go), exact bash commands to run tests, and real examples of flag patterns to reject. The test templates are copy-paste ready with clear adaptation points.

The 6-step workflow is clearly sequenced with explicit validation checkpoints — Step 5 runs tests and verifies, the 'Critical findings' section defines a stop-and-report feedback loop for exploitable techniques, and the classification table in Step 3 provides clear decision criteria for each attack category. The escalation path for failures is well-defined.

The content is well-structured with clear sections and headers, but it's a monolithic document with no references to external files for detailed content. The 'Known GTFOBins attack patterns' reference section and the detailed test patterns could be split into separate files. No bundle files are provided to support progressive disclosure, though the skill does reference external paths like resources/gtfobins/<command>.md appropriately.

The description names a specific domain (shell builtins, GTFOBins attack patterns, sandbox) and a core action (validate/ensure exploits are blocked), but it doesn't list multiple concrete actions—it's essentially one action described with context.

The description answers 'what' (validate shell builtins against GTFOBins patterns) but has no explicit 'Use when...' clause or equivalent trigger guidance, which per the rubric should cap completeness at 2—and since the 'when' is entirely missing (not even implied beyond the action itself), this scores a 1.

Includes relevant technical keywords like 'shell builtins', 'GTFOBins', 'sandbox', and 'exploit', which are terms a security-minded user might use. However, it misses common variations like 'privilege escalation', 'security audit', 'command injection', or 'LOLBAS' that users might naturally say.

This is a very specific niche—GTFOBins validation of shell builtins in a sandbox context. It is highly unlikely to conflict with other skills given the narrow and specialized domain.