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API Direct – Search Substack Notes
x402
API Direct – Search Substack Notes is a paid API for AI agents from x402.apidirect.io, paid per call via x402, $0.004/call, status unknown (last checked 2026-10-30).
Search Substack Notes by keyword, with optional AI sentiment analysis using Plutchik's Wheel of Emotions
Price / call$0.004
Success—
StatusUnknown
How this service works
Search Substack Notes by keyword.
Output
Returns a merged list of up to 12 notes per page (up to 250 pages) from Substack Notes matching the keyword. Each note includes content, author, and publication details. If sentiment analysis is enabled, each note also includes Plutchik's Wheel emotion scores, dominant emotion, emotional intensity, and polarity (positive/negative).
Example use cases
Brand mention monitoring on Substack
“Search Substack Notes for mentions of 'OpenAI' over the last few pages sorted by most recent — I want to see what writers are saying about them right now.”
Trending topic sentiment research
“Find the top Substack Notes about 'climate change' — get me 3 pages sorted by top and turn on the sentiment analysis so I can see the dominant emotions people are expressing.”
Competitive intelligence on newsletter content
“Search Substack Notes for 'interest rates' and pull 5 pages sorted by most recent so I can see what financial newsletter writers are covering this week.”
Technical details
Endpoint
GEThttps://x402.apidirect.io/v1/substack/notes?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to search the Substack Notes feed specifically — the short-form social content on Substack, distinct from full newsletter posts or author profiles. Choose this over Substack author search when you want content/notes rather than profile discovery. The optional AI emotion analysis (Plutchik's Wheel) makes it uniquely suited for sentiment research without needing a separate NLP call. Prefer it when you need paginated, high-volume keyword retrieval across Substack's notes ecosystem.
Side effects
- No results found for obscure or misspelled keywords
- Rate limiting or payment failure if insufficient USDC balance
- Requesting more pages than available results (fetching stops early)
- Query exceeds 500-character limit
- Invalid sort_by value other than 'most_recent' or 'top'
- Pages value outside 1–250 range causing validation error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object |
Tags
x402
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