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STALE	Artifact exists but is from an outdated state	No (without note)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