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api-fuzzing-bug-bounty

This skill should be used when the user asks to "test API security", "fuzz APIs", "find IDOR vulnerabilities", "test REST API", "test GraphQL", "API penetration testing", "bug bounty API testing", or needs guidance on API security assessment techniques.

51

Quality

56%

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SecuritybySnyk

Critical

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tessl review fix ./skills/api-fuzzing-bug-bounty/SKILL.md
SKILL.md
Quality
Evals
Security

Quality

Content

65%Weight 40%Scale 1-5

Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.

The body is an unusually actionable reference — concrete payloads, commands, and tooling throughout — organized into a recognizable 5-step testing workflow. Its weaknesses are structural: a 425-line monolith with no reference files, duplicated tool tables, and a workflow that lacks validation checkpoints and treats destructive techniques (DoS) without verification or scope-confirmation steps.

Suggestions

Add explicit validation checkpoints to the Core Workflow (e.g., 'confirm scope/authorization before active testing', 'verify findings by re-issuing the original request alongside the modified one', 'stop and report if DoS symptoms appear') to lift workflow clarity past the destructive/batch cap of 3.

Move the Tools Reference table and the per-vulnerability payload catalogs (bypass paths, XXE/SSRF payloads) into references/ files (e.g. tools.md, payloads.md) and keep a short overview with clearly signaled links in SKILL.md.

Remove the duplicate GraphQL Tools table (its entries are all repeated in Tools Reference) and drop the Quick Reference table whose rows restate earlier sections.

DimensionReasoningScore

Conciseness

The body is mostly terse payload tables and command blocks rather than prose, but it includes redundancy (the GraphQL Tools table duplicates entries in the Tools Reference, the Quick Reference table repeats earlier sections) and standard payload knowledge Claude already has. 'Mostly efficient but could be tightened' fits; not anchor 4 because the duplicated tables and known-basics sections are clearly trimmable.

3 / 5

Actionability

Guidance is copy-paste ready throughout: executable kiterunner and curl commands, concrete IDOR mutation payloads ({"id":[111]}, URL?id=<LEGIT>&id=<VICTIM>), SQLi test strings with expected responses (AND 1=3 -> ERROR, sleep(15) -> SLEEP), a full 403-bypass path list, and specific tool URLs. This matches 'fully executable; specific examples cover the common cases'.

5 / 5

Workflow Clarity

The Core Workflow gives a clear 5-step sequence (recon -> auth -> IDOR -> injection -> method testing), but there are no validation or verification checkpoints anywhere, and destructive/batch techniques (DoS via nested GraphQL queries, limit=9999999999, unauthenticated brute force) are presented without verification steps or scope checks. Per the rubric's cap for batch/destructive operations lacking validation, workflow clarity cannot exceed 3.

3 / 5

Progressive Disclosure

There is no bundle at all (no references/, scripts/, or assets/), so all ~425 lines live in SKILL.md, including a 20-row Tools Reference table and long per-technique payload sections that clearly belong in separate reference files. Section headers are good, matching 'some structure but content that should be separate is inline', but not anchor 4, which expects most bulk content split into clearly signaled files.

3 / 5

Total

14

/

20

Passed

Description

47%Weight 40%Scale 1-5

Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.

The description has strong, natural trigger phrases that clearly signal when to invoke the skill, but it never says what the skill actually does. Adding a concrete capability statement (e.g., enumerating API endpoints, testing for IDOR/auth bypass/injection, and providing payload and tool references) would raise both specificity and completeness substantially.

Suggestions

Add a leading 'what' clause before the trigger list, e.g. 'Tests REST, SOAP, and GraphQL APIs for IDOR, authentication bypass, injection, and misconfiguration vulnerabilities. Use when...' — this alone would lift completeness from 2 to 4-5.

Include a few more natural trigger variations such as 'API pentest', 'API security audit', or 'BOLA testing' to round out trigger coverage.

Drop the filler opener 'This skill should be used when the user asks to' in favor of the conventional third-person 'Use when...' construction to tighten the description.

DimensionReasoningScore

Specificity

The description names the domain (API security) but states no concrete actions the skill performs — it is entirely a list of quoted user trigger phrases ("test API security", "fuzz APIs") with no capability statement. This matches 'names the domain but actions are minimal or generic', not the level above, which requires 1-2 concrete actions the skill actually carries out.

2 / 5

Completeness

Only 'when' is present ("This skill should be used when the user asks to...") — there is no 'what' statement describing what the skill does. This exactly matches anchor 2 ('only when is present without what') and cannot reach anchor 3, which requires a clear description of the skill's function.

2 / 5

Trigger Term Quality

Seven natural quoted phrases ("test API security", "fuzz APIs", "find IDOR vulnerabilities", "test REST API", "test GraphQL", "API penetration testing", "bug bounty API testing") give good keyword coverage users would naturally say. Falls just short of anchor 5 because common variations like 'API pentest', 'API security audit', or 'SOAP testing' are missing.

4 / 5

Distinctiveness Conflict Risk

Terms like "find IDOR vulnerabilities", "test GraphQL", and "fuzz APIs" carve a clear API-security niche, but broader phrases like "test API security" and "API penetration testing" could overlap with a general web-application pentesting skill — 'mostly distinct; minor overlap risk', one notch below the fully distinct anchor 5.

4 / 5

Total

12

/

20

Passed

Validation

100%

Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.

Validation — 16 / 16 Passed

Validation for skill structure

No warnings or errors.

Repository
zebbern/claude-code-guide
Reviewed

Table of Contents

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