Substack API

Use Substack's unofficial cookie-authenticated API to read posts, create drafts, publish issues, and manage publications on behalf of a logged-in Substack user. Required when the user asks to post to Substack, schedule a Substack send, mirror content to Substack, or extract data from a Substack account.

6 starsSoftware Development

Install

skills CLI (Claude Code, Cursor, Codex and more)

npx skills add AnthonyDavidAdams/substack-api-reference --skill substack-api

Manual install

git clone --depth 1 https://github.com/AnthonyDavidAdams/substack-api-reference.git /tmp/substack-api-reference
mkdir -p ~/.claude/skills
cp -r /tmp/substack-api-reference/. ~/.claude/skills/substack-api

Personal skills live in ~/.claude/skills. Use .claude/skills in a project folder to share a skill with your team.

From the SKILL.md

# Substack API Skill

You can drive Substack programmatically using their internal cookie-authenticated
API. There is no public API key program — auth is the session cookie a normal
browser uses.

## When to use this skill

Trigger phrases (not exhaustive):
- "post to Substack" / "send via Substack"
- "create a draft in [my Substack]"
- "publish to {publication}.substack.com"
- "import my Substack subscribers"
- "read my Substack posts"
- "schedule a Substack send"

## Before you do anything

You need TWO pieces of state from the user:

1. **Session cookie** — `connect.sid` value (or `substack.sid` on older
   accounts). See `AUTH.md` for how to obtain.
2. **Publication subdomain** — e.g. `yournewsletter` (NOT the full URL).
   Get this from `/api/v1/user/profile/self` if not supplied.

Always confirm both before making mutating calls. If the user supplied a URL
like `https://yournewsletter.substack.com`, parse out the subdomain.

## Canonical request shape

```
Cookie: connect.sid=<value>; substack.sid=<value>
User-Agent: Mozilla/5.0
```

`Mozilla/5.0` is enough — default Node/Python User-Agents get 403'd.

## The five operations you'll actually do

### 1. Validate a cookie + discover the user's publications

```http
GET https://substack.com/api/v1/user/profile/self
```

Returns `{id, handle, publicationUsers: [{publication: {id, name, subdomain}, role, is_primary}]}`.
- Any 200 = cookie valid
- 401 = cookie expired or wrong

Read the full skill on GitHub

Details

Skill name: substack-api
Repository: AnthonyDavidAdams/substack-api-reference
License: MIT
Repo updated: 23 June 2026

FAQ

What does the Substack API skill do?

How do I install the Substack API skill?

skills CLI (Claude Code, Cursor, Codex and more): npx skills add AnthonyDavidAdams/substack-api-reference --skill substack-api. Skills go in ~/.claude/skills (personal) or .claude/skills (project), and Claude loads them automatically when a task matches the description.

Is Substack API popular?

It lives in AnthonyDavidAdams/substack-api-reference, which has 6 GitHub stars and 0 forks.

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