presskit-mcp

A Python FastMCP server and CLI for publishing to Medium and Substack.

Stability warning: Both integrations rely on unofficial/deprecated access paths. Medium's REST API is frozen (no new tokens issued). Both platforms' internal endpoints are undocumented and may change without notice.

Install

pip install -e .

This installs two commands:

presskit — CLI for direct publishing from the terminal
publishing-mcp — MCP server for use with Claude Desktop/Claude Code

CLI Usage (`presskit`)

Publish a markdown file

# Publish to Medium as a draft
presskit publish medium --file docs/drafts/my-article.md

# Publish to Substack as a draft
presskit publish substack --file docs/drafts/my-article.md

# Publish to both platforms at once
presskit publish both --file docs/drafts/my-article.md

# Publish live (not draft)
presskit publish medium --file article.md --status public --tags "python,automation"

# Substack: publish to web only (no subscriber email)
presskit publish substack --file article.md --status public --no-email

The CLI reads YAML frontmatter from the markdown file:

---
title: "My Article Title"
subtitle: "Optional subtitle for Substack"
tags: [python, automation, infrastructure]
---

# My Article Title

Article body here...

If no frontmatter title is present, the first # Heading is used.

List posts

# List your Medium posts
presskit list medium --username alexander.g.moore1

# List Substack posts
presskit list substack --subdomain alexgmoore

# List Substack drafts
presskit drafts substack

CLI options reference

presskit publish <platform> [options]
  --file, -f       Markdown file to publish (required)
  --status, -s     draft | public | unlisted (default: draft)
  --tags, -t       Comma-separated tags, e.g. "python,devops" (Medium)
  --subtitle       Post subtitle (Substack)
  --no-email       Publish to web only, skip subscriber email (Substack)

presskit list <platform> [options]
  --username, -u   Medium username without @ (Medium)
  --subdomain, -d  Substack subdomain (Substack)
  --limit, -n      Max results (default: 10)

presskit drafts substack

MCP Server Usage

Run the server

# Direct
python server.py

# Or via installed entry point
publishing-mcp

Add to Claude Code (project-level)

Create .claude/mcp.json in your project:

{
  "mcpServers": {
    "publishing": {
      "command": "python3",
      "args": ["/absolute/path/to/presskit-mcp/server.py"],
      "env": {
        "MEDIUM_SESSION_COOKIE": "your_sid_cookie",
        "MEDIUM_AUTH_STATE_FILE": "/path/to/medium-auth.json",
        "SUBSTACK_EMAIL": "you@example.com",
        "SUBSTACK_PASSWORD": "your_substack_password",
        "SUBSTACK_PUBLICATION_URL": "https://yourpub.substack.com"
      }
    }
  }
}

Add to Claude Desktop

Edit ~/Library/Application Support/Claude/claude_desktop_config.json (Mac):

{
  "mcpServers": {
    "publishing": {
      "command": "python",
      "args": ["/absolute/path/to/presskit-mcp/server.py"],
      "env": {
        "MEDIUM_SESSION_COOKIE": "your_sid",
        "MEDIUM_AUTH_STATE_FILE": "/path/to/medium-auth.json",
        "SUBSTACK_EMAIL": "you@example.com",
        "SUBSTACK_PASSWORD": "your_password",
        "SUBSTACK_PUBLICATION_URL": "https://yourpub.substack.com"
      }
    }
  }
}

Restart Claude Desktop/Code after adding the config.

FastMCP Development & Testing

presskit-mcp is built on FastMCP. Here's how to work with it during development.

Inspect tools interactively

The MCP Inspector opens a browser UI where you can call any tool, see inputs/outputs, and debug:

# Using the mcp CLI (installed with mcp[cli])
mcp dev server.py

This starts the server and opens an interactive inspector at http://localhost:5173. You can:

Browse all 15 registered tools
Fill in parameters and execute them
See JSON responses in real-time
Test error handling

Run the server with stdio transport (default)

# FastMCP defaults to stdio transport (what Claude Desktop/Code expects)
python server.py

Run with SSE transport (for remote/HTTP access)

# Start as an HTTP server on port 8000
mcp run server.py --transport sse --port 8000

Then connect from any MCP client using http://localhost:8000/sse.

Call a tool directly via `mcp call`

# One-shot tool invocation without starting a persistent server
echo '{"username": "alexander.g.moore1", "limit": 5}' | \
  mcp call server.py medium_list_posts

List all registered tools

mcp tools server.py

Environment variables for testing

# Medium (session-based — no integration token needed)
export MEDIUM_SESSION_COOKIE="your_sid_value"
export MEDIUM_AUTH_STATE_FILE="/path/to/medium-auth.json"

# Medium (REST API — only if you have an existing token)
export MEDIUM_INTEGRATION_TOKEN="your_token"

# Substack
export SUBSTACK_EMAIL="you@example.com"
export SUBSTACK_PASSWORD="your_password"
export SUBSTACK_PUBLICATION_URL="https://yourpub.substack.com"

Running tests

python3 -m unittest discover -s tests -v

Tests use sys.modules patching to stub third-party deps — no external services needed.

Tools Reference

Medium (6 tools)

Tool	Auth	Method
`medium_get_current_user`	Integration token	REST API
`medium_get_publications`	Integration token	REST API
`medium_create_post`	Integration token	REST API
`medium_create_post_session`	Session cookie	GraphQL + Delta OT
`medium_list_posts`	Session cookie	Unofficial GraphQL
`medium_get_post_stats`	Session cookie	Unofficial GraphQL

Substack (9 tools)

Tool	Auth	Method
`substack_get_publication_info`	Email/password or cookie	python-substack
`substack_get_all_publications`	Email/password or cookie	python-substack
`substack_list_posts`	None (public)	Raw HTTP
`substack_get_post`	None (public)	Raw HTTP
`substack_search_publications`	None (public)	Raw HTTP
`substack_get_subscriber_count`	Email/password or cookie	python-substack
`substack_list_drafts`	Email/password or cookie	python-substack
`substack_create_draft`	Email/password or cookie	python-substack
`substack_publish_post`	Email/password or cookie	python-substack

Credentials

Medium no longer issues API tokens. The session-based tools use browser cookies:

Log in to medium.com in a browser
Extract the sid cookie from DevTools → Application → Cookies
For full functionality, save the complete browser state with playwright-cli state-save medium-auth.json and set MEDIUM_AUTH_STATE_FILE

Substack

Use your Substack email and password directly. If your account uses magic links only:

Sign out of Substack
Click "Sign in with password"
Click "Set a new password"

Architecture

presskit-mcp/
├── server.py          # FastMCP server entry point (15 tools)
├── cli.py             # CLI entry point (presskit command)
├── medium/
│   ├── client.py      # REST API + GraphQL + Delta OT HTTP layer
│   └── tools.py       # 6 MCP tools with Pydantic input models
├── substack/
│   ├── client.py      # python-substack wrapper + raw HTTP
│   └── tools.py       # 9 MCP tools with Pydantic input models
├── tests/
│   └── test_static.py # Unit tests (no external deps needed)
├── pyproject.toml     # pip installable, entry points
└── config.yaml        # Credential reference (not loaded by code)

How Medium session publishing works

Medium's web editor saves content via a delta-based Operational Transform system — not GraphQL or REST. The medium_create_post_session tool replicates this:

GraphQL createPost → creates an empty draft, returns post_id
POST /p/{post_id}/deltas → writes title + paragraphs as OT deltas
GraphQL setPostTags → sets up to 5 tags
GraphQL publishPost → publishes (optional)

This was discovered by decompiling Medium's Android APK and capturing network traffic from the web editor.

Known limitations

Medium session cookies expire — you'll need to refresh medium-auth.json periodically (re-login via browser)
Medium REST API — No new integration tokens. Only existing holders can use medium_create_post
Medium inline formatting — Bold/italic markup positions in the delta API need accurate character offsets; the current markdown parser sends plain text paragraphs
Substack — No official API. All endpoints are reverse-engineered. Keep requests under 1/sec
Images — Neither platform supports programmatic inline image upload via these tools yet