Substack MCP Server
A Model Context Protocol (MCP) server for Substack integration with Claude Code and other MCP-compatible AI tools.
Features
- Create and manage drafts - Create, update, and publish Substack posts programmatically
- Image upload - Upload images to Substack's CDN with proper metadata
- Live blogging - Real-time post updates with timestamps
- Notes - Post short-form content to Substack Notes
- Full ProseMirror support - Proper document structure for Substack's editor
Installation
# Clone the repo
git clone https://github.com/acolle/substack-mcp.git
cd substack-mcp
# Install dependencies
pip install -r requirements.txt
Setup
1. Get your Substack credentials
- Go to your Substack dashboard in Chrome/Safari
- Open DevTools (Cmd+Option+I or F12)
- Go to Application tab → Cookies → your-substack.substack.com
- Find
substack.sidand copy its value
2. Create credentials file
# Create ~/.substackrc
cat > ~/.substackrc << 'EOF'
export SUBSTACK_PUBLICATION="your-publication.substack.com"
export SUBSTACK_SID="your-cookie-value-here"
EOF
3. Add to Claude Code
# Add the MCP server to Claude Code
claude mcp add substack \
--command "bash" \
--args "-c" "source ~/.substackrc && python3 $(pwd)/substack_mcp/server.py"
Or manually add to ~/.claude.json:
{
"mcpServers": {
"substack": {
"command": "bash",
"args": ["-c", "source ~/.substackrc && python3 /path/to/substack-mcp/substack_mcp/server.py"]
}
}
}
Available Tools
| Tool | Description |
|---|---|
substack_create_draft | Create a new draft post |
substack_update_draft | Update an existing draft |
substack_append_to_draft | Append content (for live blogging) |
substack_add_code_block | Add a code block to a draft |
substack_add_image | Add an image to a draft |
substack_publish | Publish a draft |
substack_post_note | Post a short note |
substack_get_drafts | List all drafts |
substack_get_posts | List published posts |
substack_live_blog_start | Start a live blogging session |
substack_live_blog_end | End live blogging session |
Usage Examples
Create a post with Claude Code
You: Create a new Substack post about AI tools
Claude: I'll create a draft for you...
[Uses substack_create_draft tool]
Created draft 12345. Edit at: https://your-pub.substack.com/publish/post/12345
Upload and embed images
You: Add this diagram to my post [image path]
Claude: I'll upload the image and add it to your draft...
[Uses substack_add_image tool]
Image added successfully.
Live blogging
You: Start a live blog for the product launch
Claude: Starting live blog session...
[Uses substack_live_blog_start tool]
Live blog started. I'll append updates as they happen.
API Reference
SubstackClient
The core client for interacting with Substack's API.
from substack_client import SubstackClient, SubstackDocument
client = SubstackClient(token="your-sid", publication="your-pub.substack.com")
# Upload an image
img = client.upload_image("/path/to/image.png")
# Returns: {"url": "https://...", "width": 800, "height": 600, "bytes": 12345, "contentType": "image/png"}
# Create a document
doc = SubstackDocument()
doc.heading("My Post", level=2)
doc.paragraph("Hello world!")
doc.image(src=img['url'], width=img['width'], height=img['height'],
bytes_size=img['bytes'], content_type=img['contentType'])
# Create and publish
draft = client.create_draft(title="My Post", body=doc)
client.publish_draft(draft.id, send_email=False)
Key Technical Details
Image Node Structure
Substack uses ProseMirror and requires specific attributes for images:
{
"type": "captionedImage",
"content": [{
"type": "image2",
"attrs": {
"src": "https://substack-post-media.s3.amazonaws.com/...",
"width": 800,
"height": 600,
"bytes": 12345,
"type": "image/png",
"internalRedirect": "https://pub.substack.com/i/{draft_id}?img={encoded_url}",
"belowTheFold": false,
"topImage": false,
"isProcessing": false
}
}]
}
The internalRedirect field is required - without it, Substack's editor fails to render the document.
Credits
License
MIT
Disclaimer
This uses Substack's unofficial/internal API which may change without notice. Use at your own risk.