factcheck

Blog Fact-Check

Verify statistics, claims, and source attributions in blog posts.

Workflow

Step 1: Read the Blog Post

Read the target file and identify all sections containing data claims.

Step 2: Extract Statistical Claims

Scan the full text for every claim that includes a number, percentage, dollar amount, or named source. Build a claims list with these fields:

Field	Description
claim_text	The exact sentence or phrase containing the statistic
value	The numeric value (e.g., "42%", "$1.2M", "3x")
attribution	Named source if present (e.g., "HubSpot", "Gartner 2025")
url	Cited URL if present
location	Heading or line number where the claim appears

Step 3: Verify Cited Claims

For each claim that includes a URL:

1. Fetch the source page via WebFetch
2. Search the returned content for the specific numeric value
3. If exact value found, check surrounding context matches the claim topic
4. Assign a confidence score

Process claims sequentially to avoid rate-limiting source sites.

Step 4: Flag Uncited Claims

For claims without a URL:

• Mark status as UNVERIFIED
• Suggest a search query the user can run to find a source

Step 5: Generate Verification Report

Verification Scoring

Score	Status	Criteria
1.0	VERIFIED	Exact number found on cited page in matching context
0.7-0.9	PARAPHRASE	Similar data found but with different wording, rounding, or timeframe
0.3-0.6	WEAK	Source page exists and covers the topic but the specific statistic is not visible
0.0	NOT FOUND	Cited page does not contain the claimed data anywhere
N/A	UNVERIFIED	No source URL provided for the claim

Output Format

Verification Report: [Post Title]

File: [path] Claims found: [total] Verified: [count] | Paraphrase: [count] | Weak: [count] | Not Found: [count] | Unverified: [count]

#	Claim	Source URL	Score	Status	Notes
1	"73% of marketers..."	https://example.com/report	1.0	VERIFIED	Exact match found
2	"5x ROI improvement"	https://example.com/study	0.8	PARAPHRASE	Source says "nearly 5x"
3	"60% prefer video"	(none)	N/A	UNVERIFIED	Try: "video preference statistics 2025"

Recommended Actions

• [List claims that need source URLs]
• [List claims with weak or not-found scores that need replacement sources]

Limitations

• Paywalled content: WebFetch cannot access content behind login walls. Score as WEAK (0.5) with a note.
• Dynamic pages: JavaScript-rendered content may not be available via WebFetch.
• PDF sources: WebFetch may not extract PDF text reliably. Flag for manual verification.
• Archived pages: If a URL returns 404, suggest checking web.archive.org.
• Rate limits: Process no more than 10 URLs per run. If a post has more than 10 cited URLs, verify the first 10 and list the remainder as SKIPPED.