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API Direct – Substack Publication Lookup
x402
API Direct – Substack Publication Lookup 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).
Retrieve detailed metadata about a Substack publication by its subdomain, custom domain, full URL, or numeric publication ID.
Price / call$0.004
Success—
StatusUnknown
How this service works
Get a Substack publication by subdomain, custom domain, URL or ID.
Output
Returns structured metadata about the matched Substack publication, including its publication ID, name, subdomain, custom domain (if any), and other profile information such as description, author details, and subscriber-related fields.
Example use cases
Resolve custom domain to publication ID
“I have a newsletter at www.lennysnewsletter.com — can you find its Substack publication ID so I can use it in other API calls?”
Verify a Substack newsletter exists
“Can you check whether there's actually a Substack publication at the subdomain 'stratechery' and pull back whatever details are available?”
Enrich newsletter data from a URL
“I found a Substack post at https://every.to/chain-of-thought — can you look up the publication behind that URL and get me the publication name and ID?”
Technical details
Endpoint
GEThttps://x402.apidirect.io/v1/substack/publication?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to resolve a Substack newsletter's identity — converting a subdomain, custom domain, URL, or numeric ID into full publication metadata. It is the right choice when you have a partial identifier (e.g. just a domain from a link) and need the canonical publication ID for use in downstream Substack API calls, or when you want to verify that a given Substack publication exists and retrieve its profile details.
Side effects
- Publication not found for the given subdomain or domain — returns an error or empty result
- Invalid or malformed URL/subdomain input — may return a validation error
- Numeric publication_id does not correspond to any known publication — returns not-found error
- Neither publication nor publication_id provided — request rejected due to missing required parameter
- Rate limiting or payment failure (x402 payment not processed) — returns 402 Payment Required
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object |
Tags
x402
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