Posting Substack Notes every day is the new growth tax. Stay consistent and your subscribers climb. Go quiet for four days and the feed forgets you exist. The problem is that consistency by hand is a grind, and there is no official Substack API to take the grind off your plate. This guide is about closing that gap: connecting Substack to Claude (or ChatGPT) with the SubflowAI Substack MCP server, so writing, scheduling, repurposing, and even whole multi-step workflows happen inside one conversation.
We run our own GenAI Unplugged publication on exactly this setup. What used to be a 45-minute Sunday scheduling session is now a two-minute chat. Below is the full picture: the problem in detail, the two ways to connect (one of which needs no cookie at all), every tool you get grouped by the job it does, the end-to-end workflows that chain those tools for you, and the copy-paste prompts that make it useful on day one.
Note: The SubflowAI Substack MCP server is an unofficial, independent tool built by GenAI Unplugged. It is not affiliated with, endorsed by, or approved by Substack, Inc. Substack has no official public API, so this server talks to Substack's internal endpoints on your behalf. Use it at your own risk. "Substack" is a trademark of Substack, Inc., used here only to describe compatibility.
The real problem: the daily Notes tax
Here is what the growth advice leaves out. "Just post Notes every day" sounds free. It is not. Doing it properly is a real, recurring cost, and it compounds in four places.
Writing. A good Note is not a status update. It has a hook, a shape, and a reason to be reshared. Coming up with five or seven of those a week, in your voice, without repeating yourself, is genuine creative work. Most people run dry by Wednesday and start posting filler, which trains the algorithm to show them less.
Scheduling. Say you do write seven Notes. Now you open the composer seven times, paste each one, pick a time, and confirm. Then you do it again next week. Twenty-one Notes a week is roughly three and a half hours of copy, paste, pick a time, repeat. It is the least creative part of the job and it eats the most clock.
Timing. When should each Note go out? You are guessing. You do not have your open slots in front of you, so you cluster three on Monday and leave Thursday empty, or you double-book the same 9am twice and one silently loses. A calendar you cannot see is a calendar you fill badly.
Everything after. The replies pile up and you answer the loudest ones instead of the most valuable. The analytics that would tell you which angle actually worked sit behind a stats page you never open. Your best article from last month never gets turned into the ten Notes it could have become. The work you already did stops paying you back.
And there is no official Substack API to automate any of this. So the tools that exist are a compromise. Browser extensions click around the page for you but only really solve scheduling. Open-source developer scripts can do more, but you have to clone a repo, run a server, and keep it alive. Neither one lets you say what you want in plain English and have it happen.
That is the gap the SubflowAI Substack MCP server fills.
The short answer
The SubflowAI Substack MCP server is a hosted server that connects Claude (Desktop, Cowork, or Code) and ChatGPT to your Substack. Once linked, an AI assistant can write and schedule Notes, plan them into your open calendar slots, repurpose an article into a batch of Notes, draft full articles, read your real stats, and run whole multi-step workflows, all from a normal conversation. It never touches your password. You connect either by pairing the SubflowAI browser extension (no cookie paste) or by adding your own session cookie to your config. The core tools are free for GenAI Unplugged subscribers, and setup takes about five minutes with no code.
Why this exists: Substack has no official API
Here is the load-bearing fact. Substack does not publish an official API. There is no documented, supported way for an outside app to post a Note or pull your stats. That is why most "Substack automation" lives in browser extensions that click around the page for you, or in developer scripts you have to clone and run yourself.
An MCP server is a cleaner answer. MCP, the Model Context Protocol, is the standard way to give an AI assistant new tools. A SubflowAI Substack MCP server exposes a set of Substack actions as tools the assistant can call. You ask in plain English, the assistant calls the tool, and the action happens in your Substack. No clicking, no scripts, no terminal.
The version covered here is hosted, so you do not run anything. You point your AI client at it, authenticate once, and the tools show up inside your conversation.
Two ways to connect: relay or cookie
This is the part most write-ups skip, and it is the most important choice you make. There are two connection modes. They unlock different tools and suit different people.
The SubflowAI relay: "Connect to Claude" (no cookie paste)
This is the path we recommend, and the one that unlocks the most. You install the SubflowAI Chrome extension, open its Connect to Claude panel, and it shows you a short pair code. You give that code to your AI client once. From then on, when Claude or ChatGPT wants to do something on your Substack, the command is relayed into your own browser and runs there, using the Substack session you are already logged into.
Two things make this special. First, your Substack login never leaves Chrome. There is no cookie to copy, nothing sensitive sits in a config file, and you can cut every agent off with one button in the extension. Second, because it runs inside SubflowAI, it unlocks the tools that only SubflowAI has: your real posting calendar, free-slot planning, and AI repurposing in your brand voice. The trade-off is that your browser has to be open with the extension connected, since that is where the work actually happens.
Bring your own cookie: the standalone path
The alternative is to paste your own substack.sid session cookie into your MCP config. Now the server can talk to Substack directly, using your cookie, even with your browser closed. This is the right choice if you want a headless setup for a 24/7 cloud agent, or you just prefer configuring things by hand. You get the full set of standard Substack actions: writing, scheduling, drafts, and analytics. You do not get the SubflowAI-only calendar and AI tools, because those live inside the extension.
Most creators want the relay. Builders running headless agents want the cookie. Here is the quick comparison.
| SubflowAI relay ("Connect to Claude") | Bring your own cookie | |
|---|---|---|
| Setup | Pair a short code, no paste | Paste your substack.sid cookie |
| Your login | Never leaves your browser | Lives in your local config |
| Browser | Must be open and connected | Can be closed (runs headless) |
| Calendar + AI tools | Yes | No |
| Standard Notes, drafts, analytics | Yes | Yes |
| Best for | Most creators | Headless and cloud agents |
You can read the fully guided version, with screenshots, in Connect SubflowAI to Claude and ChatGPT, step by step.
What you can do: every tool, grouped by job
The server gives your assistant a focused set of tools. Here is what they do, organized by the job you are trying to get done, with an example prompt for each group.
Write and schedule Notes
These are the workhorse tools. Claude can create a Note as a draft, schedule it for a future time, publish it now, edit the text of an existing Note, or delete one. There is also a bulk scheduler built for queueing a whole week of Notes in a single pass, throttled so it never looks like a bot.
"Write five Substack Notes from my last article, space them across the next five weekdays at 9am, and schedule them all."
Claude drafts the Notes, shows you the schedule, and on your go-ahead calls the scheduler so they land in your Substack queue. No copy and paste.
Plan your calendar (SubflowAI relay)
This is where the relay earns its keep. Because SubflowAI knows your real posting slots and your existing queue, Claude can see your calendar the way you do. It can tell you how full next week is, list your exact open times, and plan a batch of Notes into those open slots without you eyeballing anything. It never schedules on its own, it hands you a plan to approve.
"Is my calendar full next week? Show me the open slots, then plan these five Notes into them, one per day."
Repurpose and refine with AI (SubflowAI relay)
Paste in an article, or point Claude at your latest post, and the AI repurposing tool turns it into several standalone Notes in your configured brand voice, using your own SubflowAI credits. A second tool punches up any single Note, shorter, sharper, more likely to get reshared. This is the loop that turns one piece of work into a week of Notes.
"Repurpose my latest newsletter into five Notes in my voice, make the second one punchier, then schedule the batch across next week."
Read and analyze your Notes
Claude can list your recent Notes with their engagement and pull the detail of any single Note, including reactions, restacks, and replies. That turns "which of my Notes actually worked" into a question you can just ask.
"List my Notes from the last two weeks and tell me which angle got the most restacks."
Check your dashboard and subscriber stats
Claude can read your publication dashboard, your subscriber totals (free and paid), and, on the paid tier, your growth over time and per-post traffic, without you opening the Substack stats page.
"What are my current subscriber numbers, how many are paid, and which post this week got the most opens?"
Draft and update full articles from Claude Cowork
This is the part no Notes scheduler does. Claude can create a full article draft in your Substack and update an existing one: title, subtitle, body, and section. Pair it with Claude Cowork and you can go from an outline to a finished draft sitting in your Substack, ready for your review. It never hits publish for you, so you always get the last look.
"Turn this outline into a full Substack draft in my publication, set the subtitle, and leave it unpublished for me to review."
Write in our proven Note formats
The server also ships our content playbook as a tool, so Claude does not start from a blank page. The viral_notes_creator tool hands Claude 13 named Note formats, think Contrarian Take, Permission Slip, and the Screenshot-Worthy Truth Bomb, plus 10 more, each with the rules behind why it performs and a paste-ready prompt. Those formats and their rules were built from an analysis of thousands of high-performing Substack Notes, and they live inside the tool rather than on this page. Ask Claude for a format, write the Note, then schedule it. That is the loop nothing else closes: generate in a proven format, then schedule, in one conversation.
Two more content tools come along free: substack_toc builds a numbered table of contents with working anchor links for a long article, and substack_live_recap turns a Substack Live transcript into a publish-ready recap. viral_title_variants (PluggedIn) generates a ranked set of high-CTR titles grounded in our own best performers.
Run whole workflows, not just single tools
Single tools are useful. The thing that actually saves your Sunday is the substack_workflow tool, which ties the rest together. Instead of you remembering which tools to chain and in what order, Claude asks the server for a playbook and runs the whole flow, pausing for your approval before anything goes live. You say the goal in plain language, and the assistant handles the sequence. Three workflows are live today.
Fill my calendar with Notes
You say how many Notes you want and roughly what about. Claude pulls a proven format, drafts the batch in your voice, checks how full your calendar is, finds your genuinely open slots, and lays out a schedule with every Note and its time. Nothing is booked until you say yes. Then it bulk-schedules the lot and reads the queue back so you can confirm.
"Fill my calendar with five Notes for next week about AI writing, then show me the plan before scheduling."
This is the flagship. It collapses the entire write-plus-schedule chore, the one that used to eat 45 minutes, into a single approved conversation.
Insert a table of contents into an article
Long Substack posts read better with jump links, but building anchored navigation by hand is fiddly. Claude reads your article, builds a numbered table of contents using Substack's own anchor pattern, shows you a preview first, and only then writes it into the draft. If the post is already published, it pushes the change live silently, with no email to your subscribers. The rest of the body, including your subscribe boxes and buttons, is never touched.
"Add a table of contents to my latest published article, and update it without emailing my list."
Repurpose an article into scheduled Notes
The win-back for work you already did. Point Claude at a post, and it turns it into several Notes in your voice, lets you sharpen the ones you like, finds your open slots, and schedules the batch. One article becomes a week of Notes, start to finish, in one thread.
"Repurpose my top post from last month into four Notes and schedule them two days apart."
A fourth workflow, triaging the people who reply to you and drafting responses, is on the way. Every workflow stops for your approval before it schedules or publishes, so the assistant plans and you decide.
Real use cases: who this is for
Different creators lean on different parts of this. Here is where it pays off, with the prompts that earn their keep.
The daily poster who is burning out. You know Notes drive growth, but the daily grind is wearing you down. The fill-my-calendar workflow is your relief valve: one approved chat on Sunday queues the whole week.
"Read my latest article, write seven Notes across different angles, and schedule one per weekday at 9am."
The newsletter writer sitting on a back catalog. You have dozens of good posts that stopped working the day after they went out. Repurposing turns each one back into a week of Notes.
"Pull my three best posts from this quarter and turn each into a batch of Notes, scheduled across the next three weeks."
The busy operator who wants the numbers. You do not want to live in the stats page, you want the one-line read on Monday morning.
"Give me my subscriber totals, my best post this week by opens, and which Note got the most replies."
The builder wiring up an agent. You want a headless setup that runs on a schedule with the browser closed. The bring-your-own-cookie path is yours: standalone, no extension required.
"Every Monday at 8am, draft five Notes from last week's post and schedule them across the week."
The long-form publisher. You write real articles and want them to look the part, with navigation and strong titles.
"Add a table of contents to this draft, then give me eight title options ranked by likely click-through."
Ready to connect Substack to Claude?
Free for GenAI Unplugged subscribers. No terminal, no code, about five minutes to set up.
Connect Substack to ClaudeFree vs PluggedIn: what each tier unlocks
The server is tiered to your GenAI Unplugged subscription, and a paid SubflowAI license unlocks the paid tier too. Free covers everything most writers need day to day. The paid tier adds deeper analytics, AI repurposing, and full article drafting.
| Capability | Free | Paid (PluggedIn or paid SubflowAI) |
|---|---|---|
| Create, schedule, edit, publish, delete Notes | Yes | Yes |
| Bulk-schedule Notes | Up to 7 per batch | Up to 30 per batch |
| Calendar planning: capacity, free slots, distribute (relay) | Yes | Yes |
| List and read your Notes with engagement | Yes | Yes |
| Dashboard and subscriber totals | Yes | Yes |
| Viral notes creator (13 formats) | Yes | Yes |
| Substack TOC and Live recap tools | Yes | Yes |
| Workflow playbooks (fill calendar, insert TOC, repurpose) | Yes | Yes |
| AI repurpose an article into Notes (relay) | No | Yes |
| Viral title variants | No | Yes |
| Post analytics: one post, or all posts in one report | No | Yes |
| Subscriber growth, sources, and full list export | No | Yes |
| Create and update full article drafts | No | Yes |
SubflowAI Substack MCP vs the other ways to automate Substack
There is no official Substack API, so every tool works around that. Here is how the SubflowAI Substack MCP server compares to the other options, including our own SubflowAI, which is both a standalone app and the no-cookie relay for the MCP.
| Approach | Setup | Write in proven formats | Bulk schedule | Repurpose + workflows | Draft full articles | Cost |
|---|---|---|---|---|---|---|
| SubflowAI Substack MCP (this guide) | About 5 minutes, no code | Yes, 13 formats | Yes (7 free, 30 paid) | Yes, guided | Yes, from Claude Cowork | Free for subscribers |
| Open-source dev scripts | Clone a repo, run a server | No | Some | No | Read-heavy, limited | Free, you self-host |
| Notes scheduler extensions | Install a browser extension | No | Yes, notes only | No | No | Freemium |
| SubflowAI (our product) | Install, zero config | Yes, managed | Yes, visual calendar | In-app | No | Freemium |
| Doing it by hand | None | No | About 45 minutes a batch | No | No | Your time |
The short version: the dev scripts need a terminal, the Notes extensions only schedule, and doing it by hand does not scale. The SubflowAI Substack MCP is the one that writes in proven formats, plans your calendar, repurposes, and runs whole workflows, all from inside Claude or ChatGPT. If you would rather work in a visual calendar instead of a chat, SubflowAI is the done-for-you app, and it doubles as the relay that connects this MCP without a cookie.
How to connect Substack to Claude
Setup takes about five minutes. The relay is the easiest path and needs no cookie; the cookie path is for headless setups. The walkthrough below covers the cookie config on screen.
Option A: the SubflowAI relay (no cookie)
- Install the SubflowAI Chrome extension and log into Substack as normal.
- Open the extension, go to Settings, and open the Connect to Claude panel. It shows a short pair code.
- In your AI client (Claude Desktop, Cowork, Code, or ChatGPT), add the SubflowAI Substack MCP server and give it the pair code when asked.
- Done. Commands now run inside your browser, and your login never leaves Chrome. The full step-by-step with screenshots lives in the SubflowAI connection guide.
Option B: bring your own cookie
You need two values, both pasted into your config once.
For the session cookie:
- Open Chrome and go to any Substack page while logged in.
- Press F12, then open the Application tab, then Cookies, then
.substack.com. - Find
substack.sidand copy its value (it starts withs%3A).
For your subdomain, look at your Substack URL. In https://yourname.substack.com, the part before .substack.com is your subdomain.
Claude Desktop or Claude Cowork. Paste this into ~/Library/Application Support/Claude/claude_desktop_config.json on macOS, or %APPDATA%\Claude\claude_desktop_config.json on Windows. It uses mcp-remote, so you need Node.js installed.
{
"mcpServers": {
"substack": {
"command": "npx",
"args": [
"-y",
"mcp-remote",
"https://substackmcp.genaiunplugged.com/mcp",
"--header",
"X-BYOK-Substack-Cookie:PASTE_YOUR_SID_HERE",
"--header",
"X-BYOK-Substack-Subdomain:PASTE_YOUR_SUBDOMAIN_HERE"
]
}
}
}
Claude Code. Paste this into ~/.claude/settings.json.
{
"mcpServers": {
"substack": {
"type": "http",
"url": "https://substackmcp.genaiunplugged.com/mcp",
"headers": {
"X-BYOK-Substack-Cookie": "PASTE_YOUR_SID_HERE",
"X-BYOK-Substack-Subdomain": "PASTE_YOUR_SUBDOMAIN_HERE"
}
}
}
}
Replace PASTE_YOUR_SID_HERE with your session cookie and PASTE_YOUR_SUBDOMAIN_HERE with your subdomain (for example, genaiunplugged).
Authenticate with a magic link
Save the config and fully restart your client. The app opens a browser window for you. Enter the email that identifies you, and we send a magic link. Click it, and you bounce back into Claude with the tools loaded. In Claude Code, run /mcp or just ask Claude to use a Substack tool, and it opens the browser for you.
One thing to get right: the email is your identity, and it decides your tier. Use either the email you subscribe to GenAI Unplugged with on Substack, or the email you bought SubflowAI with. Paid SubflowAI customers get the full paid Substack toolset this way, even without a paid GenAI Unplugged Substack subscription. Do not use the email on your Claude account. The email must match your subscription or purchase exactly.
Is it safe?
Short version: you stay in control, and your password never enters the picture.
- No password, ever. You authenticate with a magic link to your email. The server never asks for or stores your Substack password.
- On the relay, your login never leaves Chrome. Commands run inside your own browser using the session you are already in. Nothing sensitive sits in a file, and one button in the extension cuts off every connected agent.
- On the cookie path, your cookie stays on your machine. Your
substack.sidlives in your local config and is sent with each request. It is never stored or logged on the server. Log out of Substack and it stops working. - Drafts, not surprise publishes. Claude creates and updates article drafts but does not publish full articles for you. Workflows pause for your approval before anything goes live.
- Conservative limits. Because there is no official Substack API, the server keeps request limits deliberately low to protect your account from looking automated.
Troubleshooting
A few things trip people up. Most fixes take a minute.
- It will not connect, or the login page hangs. Clear the client auth cache. Fully quit Claude (not just the window), then remove the
~/.mcp-authfolder on macOS or Linux, or%USERPROFILE%\.mcp-authon Windows. Reopen and re-authenticate. - The relay says my session expired. Open substack.com, log back in, and the extension reconnects on its own. The relay only works while you are logged in.
- The same email stopped working after a few tries. The magic-link endpoint is rate limited per hour. Wait an hour, or test with a different subscriber email.
- The magic link says invalid or expired. Some corporate and .edu mail scanners pre-open links. Click the link yourself from the original email, and use the Confirm button on the page rather than relying on a preview.
- Tools do not appear. Check your config JSON is valid (no trailing commas), confirm your cookie has not expired, and make sure you fully quit and reopened the app.
Go deeper
- Connect SubflowAI to Claude and ChatGPT, step by step, the guided version that pairs the SubflowAI extension so your Substack login never leaves Chrome.
- SubflowAI: the fastest way to schedule Substack Notes if you want a done-for-you product with a visual calendar.
- The full Substack Notes workflow with Claude Cowork, the deep walkthrough this guide is built on.
- Claude Code extensions explained, the wider map of skills, MCP servers, and more.
- Browse all our products.
Frequently asked questions
Is there a Substack API?
There is no official, public Substack API. Substack has internal endpoints its own apps use, but nothing documented or supported for developers. The SubflowAI Substack MCP server is a community tool that talks to those endpoints on your behalf, so Claude or ChatGPT can read and write your Substack without an official API.
Do I have to paste my Substack cookie?
No. There are two ways to connect. The SubflowAI relay (Connect to Claude) pairs with a short code and runs every command inside your own browser, so your Substack login never leaves Chrome and you paste nothing. The alternative is bring-your-own-cookie, where you paste your session cookie into your MCP config so the server can run headless with your browser closed. Most people use the relay.
Can I use this with ChatGPT, or only Claude?
Both. Through the SubflowAI relay, the SubflowAI Substack MCP server works with Claude Desktop, Claude Cowork, Claude Code, and ChatGPT. Any MCP client that supports remote servers can drive it.
Can Claude post to Substack?
Yes. With the SubflowAI Substack MCP server connected, Claude can create, schedule, edit, publish, and delete Substack Notes directly. It can also create and update full article drafts. Claude never publishes a full article on its own, it leaves drafts for you to review and send.
What is a SubflowAI Substack MCP workflow?
A workflow is a ready-made playbook the server hands Claude so it runs a whole multi-step job, not just one tool. Ask Claude to "fill my calendar with notes" or "add a table of contents to my article" and the substack_workflow tool tells it exactly which tools to chain, in what order, pausing for your approval before anything goes live. Three are live today: fill your calendar, insert a table of contents, and repurpose an article into Notes. It is free.
Can Claude write a full Substack article?
Yes. Using Claude Cowork or Claude Desktop with the SubflowAI Substack MCP server, Claude can draft a complete article from your notes or outline and push it to your Substack as a draft. You review and publish it yourself. Full article drafting is a PluggedIn (paid) feature.
Is the SubflowAI Substack MCP server safe? Does it store my password?
It never sees or stores your Substack password. You authenticate with a magic link to your email. On the SubflowAI relay, commands run inside your own browser and your login never leaves Chrome. On the cookie path, your session cookie is sent with each request and is never stored or logged on the server. You can revoke access any time by logging out of Substack.
Is the SubflowAI Substack MCP server free?
The notes tools, the calendar planning tools, and the core read tools are free for any GenAI Unplugged subscriber. Advanced tools like subscriber growth over time, per-post analytics, AI repurposing, and full article drafting are unlocked for PluggedIn members on the paid Substack tier, or for anyone with a paid SubflowAI license.
Do I need to code to use it?
No. Either pair the SubflowAI extension with a short code, or paste one config block into Claude Desktop, Claude Cowork, or Claude Code. There is no terminal, no git clone, and no server to run. Setup takes about five minutes.
Is the SubflowAI Substack MCP against Substack's terms of service?
Substack has no official API, so any automation tool, including this one, uses internal endpoints that are not officially supported. Use it at a reasonable cadence and at your own risk. The server enforces conservative rate limits to keep activity looking human, but you are responsible for how you use it. You stay in control, and you can revoke access any time by logging out of Substack.
How many Substack Notes can I schedule at once?
On the free tier you can bulk-schedule up to 7 Notes per batch, which covers a full week one a day. PluggedIn members can bulk-schedule up to 30 in a single call. Either way the server spaces the calls out to avoid tripping Substack's bot detection.
Can I use the SubflowAI Substack MCP on the free Substack plan?
Yes. The MCP works with any Substack publication. Tiering here is about your GenAI Unplugged subscription or your SubflowAI license, not your Substack plan: the notes, calendar, and core read tools are free for any GenAI Unplugged subscriber, and advanced analytics, title variants, AI repurposing, and full article drafting unlock for paid members.
What is the viral notes creator?
It is a free tool that hands Claude 13 named Substack Note formats, each with a clear use-when and a paste-ready prompt built from an analysis of thousands of high-performing Notes. Ask Claude for a format, write the Note, then schedule it, all in one conversation. The formats and their rules live inside the tool, not on this page.