Do I need a Substack developer account?

No. There is no Substack app, OAuth flow or app review. One InsightSocial API key works for this endpoint and every other platform, and your first 10 calls priced at 100 credits or less are free.

What does one call return?

One call returns the posts in the data object of the standard response envelope. Fields the platform did not provide are listed in unavailable, so a null there means unknown, not zero.

What happens if the account is private or nothing is found?

You get an error or an empty result, and it costs 0 credits. The API reads public Substack data only, so private accounts and deleted content come back as not found rather than as partial data.

Can I call the Substack Posts API from Claude, ChatGPT or Cursor?

Yes. Add the hosted MCP server at https://api.insightsocial.app/mcp to your AI app and sign in. The assistant finds this endpoint by name, shows its price and calls it with your credits.

GET /v1/substack/posts

Substack Posts API

Returns a publication’s recent posts, or one post: title, full text and Markdown, author, reactions, comments, restacks, word count and whether it is paid.

Get a free API key Full API reference

10–120 credits, metered · single call · failed calls free · 10 free calls to start

curl "https://api.insightsocial.app/v1/substack/posts?url=https%3A%2F%2Fwww.astralcodexten.com" \
-H "x-api-key: $INSIGHTSOCIAL_API_KEY"

200 OKJSON

{
"success": true,
"platform": "substack",
"endpoint": "/v1/substack/posts",
"schema_version": "2",
"data": {
"items": [
{
"post": {
"id": "<string>",
"url": "<string | null>",
"kind": "<string | null>",
"content": {
"text": "<string | null>",
"media_urls": "<array | null>",
"thumbnail_url": "<string | null>",
"duration_seconds": "<number | null>"
},
"author": {
"id": "<string | null>",
"username": "<string | null>",
"display_name": "<string | null>",
"avatar_url": "<string | null>",
"verified": "<boolean | null>"
},
"engagement": {
"views": "<integer | null>",
"likes": "<integer | null>",
"comments": "<integer | null>",
"shares": "<integer | null>",
"saves": "<integer | null>"
},
"flags": {
"nsfw": "<boolean | null>",
"spoiler": "<boolean | null>",
"pinned": "<boolean | null>",
"deleted": "<boolean>",
"likes_hidden": "<boolean | null>",
"comments_hidden": "<boolean | null>",
"shares_hidden": "<boolean | null>",
"views_hidden": "<boolean | null>",
"saves_hidden": "<boolean | null>"
},
"published_at": "<string | null>",
"language": "<string | null>",
"ext": "<object | null>"
}
}
]
},
"unavailable": [],
"credits_used": "<integer>"
}

When to use it

Use it with a publication URL (or custom domain) for its archive, or a /p/ post URL for one post.

Parameters

Query parameters for GET /v1/substack/posts. Send your key in the x-api-key header.

Name	Required	Description
url	Yes	A Substack publication URL or custom domain, or one post URL (…/p/slug).
limit	No	Most recent posts to read, 1 to 100. Default 25. Billed per post returned.
start_date	No	Only posts published on or after this date (YYYY-MM-DD). Applied to the limit most recent posts, so raise limit to reach further back.
end_date	No	Only posts published on or before this date (YYYY-MM-DD). Applied to the limit most recent posts, so raise limit to reach further back.
only_free	No	true for free (non-paywalled) posts only.
content_type	No	Only one post type. Default all.
min_comments	No	Only posts with at least this many comments.
min_reactions	No	Only posts with at least this many reactions.
min_word_count	No	Only posts with at least this many words.
include_content	No	Include the article body (text and Markdown). Default true; false is faster.

Response fields

The same unified schema every platform returns, so code written for Substack works on the other eight. A field the platform did not provide is null and listed in unavailable.

Field	Type	Notes
id	string	An identifier, always a string. Never parse it as a number: several platforms use ids above 2^53.
url	string \| null
kind	string \| null	The format of the post. Format words only, never a platform name. short = short-form vertical video (a reel, a TikTok, a YouTube Short).
content.text	string \| null
content.media_urls	array \| null
content.thumbnail_url	string \| null
content.duration_seconds	number \| null
author.id	string \| null
author.username	string \| null
author.display_name	string \| null
author.avatar_url	string \| null
author.verified	boolean \| null
engagement.views	integer \| null	A count. null when the platform does not expose it; 0 only when it is really zero.
engagement.likes	integer \| null	A count. null when the platform does not expose it; 0 only when it is really zero.
engagement.comments	integer \| null	A count. null when the platform does not expose it; 0 only when it is really zero.
engagement.shares	integer \| null	A count. null when the platform does not expose it; 0 only when it is really zero.
engagement.saves	integer \| null	A count. null when the platform does not expose it; 0 only when it is really zero.
flags.nsfw	boolean \| null
flags.spoiler	boolean \| null
flags.pinned	boolean \| null
flags.deleted	boolean
flags.likes_hidden	boolean \| null
flags.comments_hidden	boolean \| null
flags.shares_hidden	boolean \| null
flags.views_hidden	boolean \| null
flags.saves_hidden	boolean \| null
published_at	string \| null	ISO-8601 timestamp in UTC, ending in Z.
language	string \| null	The content's language as the platform states it, e.g. en, pt-BR. Detected languages come later (§7.1).
ext	object \| null	Platform-specific fields, snake_case.

Every field, error and example is in the Substack Posts API reference.

How much does the Substack Posts API cost?

Metered: 10–120 credits a call. The ceiling is reserved when the call starts and you are charged what it actually read.

Failed calls are free
A call that errors or finds nothing costs 0 credits.
Know the price first
Add dry_run=1 and the response quotes the call without making it. Nothing is charged.
One balance
API calls and Chrome extension exports share the same credits, on the free plan too.

See plans and credit packs How credits work