Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add bdfinst/agentic-dev-team --skill feature-file-validationgit clone --depth 1 https://github.com/bdfinst/agentic-dev-teamWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/bdfinst/agentic-dev-team/feature-file-validation)<a href="https://agentmods.dev/skills/bdfinst/agentic-dev-team/feature-file-validation"><img src="https://agentmods.dev/badge/skills/bdfinst/agentic-dev-team/feature-file-validation/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/bdfinst/agentic-dev-team/feature-file-validation"><img src="https://agentmods.dev/badge/skills/bdfinst/agentic-dev-team/feature-file-validation.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00101 | $0.00833 |
| Opus 5.5 | $0.00040 | $0.00333 |
| Sonnet 5.5 | $0.00020 | $0.00167 |
| Haiku 4.5 | $0.00010 | $0.00083 |
Grade A, and why
feature-file-validation scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 79 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Feature File Validation
Feature files are the contract between intent and implementation. This skill validates two things: (1) are scenarios well-formed, deterministic, and behavioral? (2) does every scenario have matching test automation?
When to Run
- During
/code-reviewwhen.featureor step definition files are in the changeset - When
test-reviewencounters feature files - When a user explicitly asks to validate feature files or BDD scenarios
- Before
/buildas a pre-flight check
Step 1: Find Feature Files
Locate all .feature files in scope. If reviewing changed files only, limit to .feature files in the changeset plus any referenced by changed step definitions. If none found, report skip and stop.
Step 2: Validate Feature File Structure
For each feature file, check every category below. Read references/validation-rules.md for detailed patterns and examples.
| Category | What to flag | Severity |
|---|---|---|
| Gherkin syntax | Missing Given/When/Then, bad Background, empty Examples, orphan steps, blank feature name | warning |
| Determinism | Time-dependent steps, order-dependent scenarios, environment-dependent steps, probabilistic assertions, uncontrolled concurrency | error |
| Implementation coupling | Technology names, code-level details, CSS selectors, performance constraints, data structure specifics in step text | warning |
| Scenario quality | Multiple When steps, vague assertions ("it works"), missing negative/edge cases | warning/suggestion |
Step 3: Verify Test Automation Coverage
For each scenario, check whether test automation exists using two strategies. A match from either is sufficient. Read references/validation-rules.md for framework detection patterns and naming conventions.
- Strategy A — Step definition matching: Find step definition files (per framework conventions) whose patterns match the scenario's step text. Covered when all steps have definitions.
- Strategy B — Test file naming: Find test files named after the feature file (e.g.,
login.feature->login.test.ts) that reference the scenario name.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 79 lines · 101 tokens per session scan A 99c98d713bda
feature-file-validation is a skill published in the GitHub repository bdfinst/agentic-dev-team (295 stars, last pushed 4d ago), licensed MIT. It adds 101 tokens to every session and 833 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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