Evidence Verifier Skill Skill

Evidence Verifier Skill

Purpose: Ensure that claimed proof artifacts are real, accessible, and relevant. Phantom evidence is evidence that is claimed but does not exist.

When to Use

Use this skill when:

A sub-agent or specialist claims to have proof of completion
A proof artifact is referenced by path or URL but not shown
A completion claim is made without supporting evidence
You need to audit a list of claimed artifacts before accepting a milestone

Evidence Classification

| Class | Definition | Accepted? | | -------- | ------------------------------------------------ | ----------------- | | VERIFIED | Artifact shown, accessible, relevant, and recent | Yes | | CLAIMED | Artifact referenced but not shown | No | | PHANTOM | Artifact claimed to exist but cannot be found | No | | STALE | Artifact exists but is from an outdated state | No (without note) |

Procedure

Step 1: Enumerate claimed artifacts

List every artifact that has been claimed as proof:

File paths (e.g., reports/gap-analysis.md)
URLs (e.g., https://production-url.com)
Test output (e.g., "all 47 tests passing")
Screenshots (e.g., "screenshot of dashboard")

Step 2: Verify each artifact

For each claimed artifact:

If it's a file path:

Check the file exists using the Read tool or ls
Check it contains relevant content (not empty, not placeholder)
Check it was modified recently (matches claimed work)

If it's a URL:

Fetch the URL and verify the response code
Verify the content matches the claim

If it's tool output (test results, curl, etc.):

The output must be shown verbatim in the evidence
Claimed results without shown output = CLAIMED (not VERIFIED)

If it's a screenshot:

The screenshot must be viewable and show the claimed state
A description of a screenshot is not a screenshot

Step 3: Classify and report

Assign VERIFIED, CLAIMED, PHANTOM, or STALE to each artifact.

Output Format

EVIDENCE VERIFICATION REPORT
═══════════════════════════════════════════════════
Verified: [N] / [total] artifacts

ARTIFACT 1: [description]
  Type:   [file | URL | test output | screenshot]
  Claim:  [what was claimed]
  Status: VERIFIED | CLAIMED | PHANTOM | STALE
  Notes:  [what was found / what is missing]

ARTIFACT 2: [description]
  ...

VERDICT
─────────────────
If all VERIFIED:  → ACCEPT evidence
If any not VERIFIED: → REJECT — list what is needed:
  □ [artifact 1]: [exact action to produce real evidence]
  □ [artifact 2]: [exact action]
═══════════════════════════════════════════════════

Validation Gates

Before marking any artifact VERIFIED:

[ ] The artifact is shown (not referenced)
[ ] The artifact is from the correct environment (production != localhost)
[ ] The artifact covers the specific claim (not adjacent evidence)
[ ] The artifact is not a placeholder or generic example

Failure Modes

| Failure | Recovery | | ------------------------------------------- | ----------------------------------------------------- | | Artifact is a description, not the artifact | Request the actual file/output/screenshot | | File exists but is empty | Mark PHANTOM — empty files are not evidence | | URL returns 404 | Mark PHANTOM — request correct URL | | Test output shows failures | Do not reclassify as VERIFIED — failures are failures | | Screenshot is blurry or cropped | Request full clear screenshot |

Eval Examples

Good — VERIFIED

Claim: "All tests pass" Evidence shown: Full vitest output with 47 tests, 0 failures, coverage 82% Classification: VERIFIED

Bad — CLAIMED (rejected)

Claim: "All tests pass" Evidence shown: "I ran the tests and they all passed." Classification: CLAIMED — test output not shown

Agent Skills: Evidence Verifier Skill

Install this agent skill to your local

Skill Files