Substack by Cotlet

Substack API and MCP server: connect Substack to ChatGPT and Claude

Yes, ChatGPT, Claude and other AI agents can work in your Substack account. That includes Cursor, Codex, OpenClaw and any MCP client, plus automations in n8n, Make and Zapier. Ask in plain words, and the AI drafts posts from your notes, schedules them, posts Notes, answers comments and reports your subscriber and post stats. It shows you what it will do first and sends nothing to other people until you say so.

As of November 2026, this repo is the missing piece: 50 Substack tools for AI assistants and scripts.

What you can ask

*Turn essay.md into a draft for everyone and schedule it for Tuesday 8:00 New York time. Once it is out, post a Note with a link card to it.*

*Find comments on my last three posts that I have not answered and draft a short reply to each.*

*Last week's numbers: new and paid subscribers, cancellations, revenue, and opens for each post.*

*Where did my readers come from in the last 30 days?*

Two ways to get it

Cotlet is best for writers and publishers who want ChatGPT, Claude or another AI agent to work in Substack for them, with nothing to install.

[Start free at cotlet.dev →](https://cotlet.dev/signup?app=substack&utm_source=github&utm_medium=readme&utm_campaign=substack&utm_content=top-button)

Run it yourself

A Substack API and a Substack MCP server you run on your own computer, in Python, on the session of your own Google Chrome. All 50 Substack tools we run in production at Cotlet: posts and drafts from Markdown, publishing and scheduling, Notes, comments, subscribers, stats, recommendations and direct messages.

Substack has no public API to write posts, publish Notes or manage subscribers, and no official MCP server. This repo gives you both:

• MCP server for Claude Code, Claude Desktop, Cursor, Codex and any MCP client, over stdio or HTTP. Setup
• REST API on http://127.0.0.1:8787/api/v1/substack, with OpenAPI docs at /docs. Setup
• Python: call("list_posts", status="draft"), plus 14 ready scripts in examples/.

Free for your own use, your own business included (license).

uv tool install substack-api-mcp                  # or: pip install substack-api-mcp

substack-mcp connect # reads your Substack session from Chrome substack-mcp call list_posts claude mcp add substack -- uvx substack-api-mcp mcp

Contents

• Questions from Substack users
• How it works
• Requirements
• Install
• Connect your Chrome
• MCP server
• REST API
• Python and the example scripts
• All 50 tools
• Configuration
• Security and your Substack account
• Errors
• Self-hosted or hosted
• FAQ
• License

Questions from Substack users

Does Substack have an API? Only a limited one (checked 11 Oct 2026). Its Developer API looks up public creator profiles after approval, and there is no public API to write posts or Notes, manage subscribers or send email. RSS reads public posts only. This repo and Cotlet give you 50 Substack tools as a REST API and an MCP server.

Can I get a Substack API key? Not from Substack for your own account. With Cotlet you get your own API key that works with your Substack account, for scripts, n8n, Make, Zapier or any HTTP client. This repo needs no key: it runs on your computer, on your own Substack session.

Is there an official ChatGPT integration for Substack? Partly. Substack has an official Claude connector that reads your publication's data, such as subscribers, revenue and post stats. It cannot write. Cotlet adds the writing side: drafts, publishing and scheduling, Notes, comments and messages, in ChatGPT, Claude and other AI agents.

How do I connect Substack to ChatGPT? Sign up at cotlet.dev, sign in to Substack once in your Cloud Browser there, and add Cotlet to ChatGPT, following the steps in your account. Then ask ChatGPT about your Substack like you would ask an assistant. ChatGPT needs a server on the internet, so this repo alone, running on your computer, does not connect to ChatGPT.

Can ChatGPT write and schedule my Substack posts? Yes, with Cotlet. It turns your notes or a Markdown file into a Substack draft, shows it to you and publishes or schedules it after your OK. It can post a Note about it once it is out.

Can ChatGPT read my Substack stats? Yes, with Cotlet: new and paid subscribers, cancellations, revenue, opens per post and where your readers came from, in plain words.

Can I automate Substack with Zapier, Make or n8n? Substack has no official way to write posts from Zapier, Make or n8n. With Cotlet they can create drafts, publish posts and post Notes, for example from a Google Doc or an RSS feed.

Can I use it from my phone? Yes, with Cotlet: once it is set up, the ChatGPT and Claude apps on your phone can use Substack for you.

Do I need to be technical? For Cotlet, no: you sign in to Substack and add Cotlet to ChatGPT or Claude, with step-by-step instructions in your account. This repo is for people who are fine with Python and a terminal.

Is my Substack account safe? Yes. Neither Cotlet nor this repo sees or stores your Substack password. You sign in yourself, the way you always do, and the AI works on that signed-in session. Anything that reaches other people asks for your OK first: in Cotlet by default, here through your MCP client.

Is it free? This repo is free, also in your own business. Cotlet is free for 7 days with no card, then one-time credit packs from $29, no subscription. Pricing.

I manage Substack for several accounts or clients. Does that work? Yes, with Cotlet. Each Substack login gets its own connection. Write to contact@cotlet.dev and tell us how many accounts you manage.

How it works

AI agent (MCP) / script (REST, Python) ──▶ substack-mcp on your computer ──your Substack cookies──▶ substack.com

▲ substack-mcp connect ───────┘ reads them once from your Chrome (DevTools Protocol)

1. You sign in to Substack in your own Chrome, the way you always do.
2. substack-mcp connect attaches to that Chrome through the Chrome DevTools Protocol, reads the substack.com cookies and saves them to ~/.config/substack-api-mcp/session.json, readable by your user only. Substack signs in by an emailed code or link, so there is no password to see or store.
3. Every tool call is a request to Substack's own web app endpoints (substack.com/api/v1 for the reader side, yourname.substack.com/api/v1 for your publication's dashboard) with those cookies, sent with curl_cffi, which copies Chrome's TLS fingerprint. No headless browser runs.

Substack's session cookie (substack.sid) lasts about three months. When Substack signs you out, the server reads the cookies from Chrome again, if Chrome is open with remote debugging on.

Requirements

• Python 3.11 or newer.
• Google Chrome 144 or newer, signed in to Substack. Any Chrome or Chromium works with a debugging port.
• macOS, Linux or Windows.
• A Substack account. Publisher tools (posts, subscribers, stats, comments) work on the first publication your account runs as admin, owner, editor or contributor. Reader tools (feed, search, Notes, messages) work on any account.

Install

From PyPI:

uv tool install substack-api-mcp       # or: pipx install substack-api-mcp, or: pip install substack-api-mcp

substack-mcp --version

MCP clients can also run it with no install: uvx substack-api-mcp mcp.

From source:

git clone https://github.com/cotletdev/substack-api-mcp-server.git

cd substack-api-mcp-server python3 -m venv .venv . .venv/bin/activate # Windows: .venv\Scripts\activate pip install -e . substack-mcp --version

With uv: uv venv && uv pip install -e ., then uv run substack-mcp ....

Setting it up with an AI agent (Claude Code, Codex, Cursor)? Open it in this folder and ask it to set up the repo: AGENTS.md tells it every step, and it asks you only for the steps in Chrome.

To update: uv tool upgrade substack-api-mcp (or pip install -U substack-api-mcp), from source git pull && pip install -e .. We copy every change of the hosted Substack tools into this repo.

Connect your Chrome

Option A: your everyday Chrome (recommended)

1. Open chrome://inspect/#remote-debugging in Chrome and switch remote debugging on. Chrome then accepts DevTools connections from programs on this computer, and asks you before each one.
2. Make sure you are signed in at substack.com.
3. Run:

   substack-mcp connect

1. Chrome asks whether to allow the connection. Click Allow.

Saved 19 Substack cookies to /Users/you/.config/substack-api-mcp/session.json

Signed in to Substack as Maya Chen (@mayachen)

You can switch remote debugging off again afterwards. Leave it on if you want the server to pick up a new session by itself after Substack signs you out.

connect looks for Chrome's DevToolsActivePort file in the default profile folder. For Chrome Beta, Canary or a custom profile folder, pass --profile-dir " ".

Option B: a Chrome with a debugging port

Chrome does not open a debugging port on your default profile, so start a separate one, sign in to Substack there once, and connect to it:

# macOS

"/Applications/Google Chrome.app/Contents/MacOS/Google Chrome" --remote-debugging-port=9222 --user-data-dir="$HOME/.chrome-substack"

Linux

google-chrome --remote-debugging-port=9222 --user-data-dir="$HOME/.chro