Substack Publisher API

Query posts, analytics, and subscriber data from Substack's official Publisher API

GitHub

substack-publisher-mcp

MCP server for Substack's official Publisher API

License: MIT Node.js MCP

Note: This is an unofficial, community-developed tool and is not affiliated with, endorsed by, or supported by Substack, Inc.

The first MCP server for Substack's official Publisher API. Query post analytics, subscriber counts, and publication data directly from Claude, Cursor, or any MCP client.

Demo of substack-publisher-mcp in Claude Code

Why this server?

substack-publisher-mcpOther Substack MCP servers
APIOfficial Publisher APIUnofficial internal API
AuthAPI key (stable)Browser cookies (fragile)
StabilityOfficial, documented APIBreaks when Substack changes internals
Multi-publicationBuilt-in supportNot available

Prerequisites

Quick Start

1. Install

git clone https://github.com/dkships/substack-publisher-mcp.git
cd substack-publisher-mcp
npm install && npm run build

2. Configure your MCP client

Add to your client's MCP config file:

ClientConfig file
Claude Desktop (macOS)~/Library/Application Support/Claude/claude_desktop_config.json
Claude Desktop (Windows)%APPDATA%\Claude\claude_desktop_config.json
Claude Code.mcp.json in your project directory
Cursor.cursor/mcp.json
{
  "mcpServers": {
    "substack": {
      "command": "node",
      "args": ["/path/to/substack-publisher-mcp/dist/index.js"],
      "env": {
        "SUBSTACK_API_KEY": "your-api-key-here"
      }
    }
  }
}

Claude Code users: Add "type": "stdio" to the server config.

3. Start using it

Ask Claude: "Show me my recent posts" or "What are my subscriber counts for the last 30 days?"

Tools

ToolDescriptionKey Parameters
list_publicationsList configured publicationsNone
list_postsList published postsstartDate, endDate, sortBy, type, maxResults, next
get_postGet a specific post by URL slugurlSlug (required)
get_post_statsGet engagement stats for a posturlSlug (required)
get_subscriber_countsGet daily subscriber counts by typestartDate, endDate
get_subscriberLook up a subscriber by emailemail (required)

All tools accept an optional publication parameter when multiple publications are configured.

Example responses

get_subscriber_counts 
[
  {
    "date": "2025-01-15",
    "total_email_subscribers": 25000,
    "paid_subscribers": 500,
    "free_trial_subscribers": 10,
    "comp_subscribers": 50,
    "gift_subscribers": 15,
    "lifetime_subscribers": 0,
    "founding_subscribers": 25
  }
]
get_post_stats 
{
  "clicks": 320,
  "opens": 5400,
  "post_id": 12345678,
  "recipients": 10000,
  "views": 6100,
  "new_free_subscriptions": 80,
  "new_paid_subscriptions": 5,
  "estimated_revenue_increase": 400
}
list_posts 
{
  "posts": [
    {
      "title": "My Latest Post",
      "audience": "only_paid",
      "subtitle": "A deep dive into the topic",
      "postDate": "2025-01-15T12:00:00.000Z",
      "urlSlug": "my-latest-post",
      "coverImage": "https://substackcdn.com/image/..."
    }
  ],
  "next": "abc123cursor"
}

Multiple publications

If you manage multiple Substack publications, configure a separate API key for each using the SUBSTACK_API_KEY_<NAME> pattern:

{
  "mcpServers": {
    "substack": {
      "command": "node",
      "args": ["/path/to/substack-publisher-mcp/dist/index.js"],
      "env": {
        "SUBSTACK_API_KEY_MAIN": "your-main-blog-key",
        "SUBSTACK_API_KEY_TECH": "your-tech-newsletter-key",
        "SUBSTACK_API_KEY_COMPANY": "your-company-updates-key"
      }
    }
  }
}

Then specify which publication to query:

"Show me subscriber counts for main" "List recent posts from the tech publication"

Use list_publications to see all configured publication names.

Troubleshooting

IssueSolution
Unauthorized errorVerify your API key is correct. The key goes directly in the authorization header with no Bearer prefix.
Missing environment variables warningOnly configure env vars for publications you have keys for. Remove the rest.
Server won't startMake sure you ran npm run build after cloning. The server runs from dist/, not src/.
No API keys configuredSet SUBSTACK_API_KEY or SUBSTACK_API_KEY_<NAME> in your MCP client config.

API Reference

This server wraps the Substack Publisher API. See Substack's documentation for details on available data and rate limits.

Contributing

See CONTRIBUTING.md for guidelines.

License

MIT License. See LICENSE for details.

Substack is a trademark of Substack, Inc. This project is not affiliated with Substack, Inc. Use of the Substack name is for descriptive purposes only.

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