Substack Saved Posts MCP & CLI

A local, stdio-based Model Context Protocol (MCP) server and sync engine for your saved/bookmarked Substack posts.

Features

• Read & Search: Full-text search (SQLite FTS5) across saved post titles, excerpts, authors, publications, and content. Filter by publication and date ranges (published_at vs saved_at).

• Save & Unsave: Bookmark new Substack posts or unbookmark existing ones via authenticated browser sessions.

• Offline First: Fast, offline queries directly from local SQLite cache.

• Privacy & Security: Keeps session credentials local, redacting tokens from logs.

• FastMCP Protocol: Stdio MCP interface with rich tool suite and resources.

Related MCP server: Lexomni MCP

Installation with uv

uv is the recommended fast Python package manager for installing and running substack-saved-mcp.

Option A: Install System-wide as a Tool (uv tool install)

Install directly from your local repository folder:

# Navigate to the repository
cd /path/to/substack-saved-mcp

# Install system-wide into an isolated uv environment
uv tool install .

# Or install directly from a remote Git repository:
# uv tool install git+https://github.com/your-username/substack-saved-mcp.git

After installation, substack-saved-mcp is immediately available in your PATH:

# Verify installation
substack-saved-mcp --help

To update or uninstall:

# Upgrade installed tool
uv tool upgrade substack-saved-mcp

# Uninstall tool
uv tool uninstall substack-saved-mcp

Option B: Local Development / Development Environment (uv sync)

If you are developing or modifying the codebase:

# Clone and enter directory
cd substack-saved-mcp

# Install dependencies and dev tools (pytest)
uv sync --extra dev

# Run CLI commands using uv run
uv run substack-saved-mcp --help

# Run tests
uv run pytest

Quick Start

# 1. Initialize local database
substack-saved-mcp init

# 2. Authenticate with Substack (opens interactive browser window once)
substack-saved-mcp login

# 3. Sync saved posts into local cache
substack-saved-mcp sync

# 4. Search saved posts via CLI
substack-saved-mcp search "artificial intelligence"

# 5. Save or unsave a post
substack-saved-mcp save "https://example.substack.com/p/post-slug"
substack-saved-mcp unsave "https://example.substack.com/p/post-slug"

# 6. Launch stdio MCP server
substack-saved-mcp serve

Configuring MCP Clients (Claude Desktop, Goose, Cursor, etc.)

Add substack-saved-mcp to your MCP client's configuration file (e.g. claude_desktop_config.json).

Using System-Wide Installed Tool (uv tool or global binary)

{
  "mcpServers": {
    "substack-saved": {
      "command": "substack-saved-mcp",
      "args": ["serve"]
    }
  }
}

Using uv directly from the Repository Path

If you prefer running directly from your repository path without installing system-wide:

{
  "mcpServers": {
    "substack-saved": {
      "command": "uv",
      "args": [
        "--directory",
        "/path/to/substack-saved-mcp",
        "run",
        "substack-saved-mcp",
        "serve"
      ]
    }
  }
}

Frequently Asked Questions (FAQ)

Where is the database saved?

By default, the SQLite database is saved in your OS application data directory:

• Linux / macOS: ~/.local/share/substack-saved-mcp/saved_posts.sqlite
  (or $XDG_DATA_HOME/substack-saved-mcp/saved_posts.sqlite if XDG_DATA_HOME is set)

You can specify a custom database path or directory using environment variables:

export SUBSTACK_SAVED_DB_PATH="/path/to/my/custom_database.sqlite"
# or
export SUBSTACK_SAVED_DATA_DIR="/path/to/my/data_dir"

Will a browser window pop up when running as an MCP server?

No, a visible browser window will not open during normal MCP operations.

• Read & Search Tools (search_saved_posts, list_saved_posts, get_saved_post, list_publications, saved_posts_status):
  Operate 100% offline using the local SQLite database. Zero browser activity.

• Sync & Write Tools (sync_saved_posts, save_post, unsave_post):
  Run in headless background mode using the pre-authenticated session stored in storage_state.json.

• Interactive Login:
  A visible browser window opens only when you manually run substack-saved-mcp login from your terminal. If your session expires while using an MCP client, the tool will return a clear error message instructing you to re-authenticate via substack-saved-mcp login instead of popping open a browser window unexpectedly.

What if I get a Playwright "Executable doesn't exist" error?

If you encounter an error like BrowserType.launch: Executable doesn't exist when running commands (especially login), it means Playwright hasn't installed its required browsers in the isolated environment.

To fix this, you need to run the playwright install command inside the environment where the tool is installed.

For a system-wide tool installation (via uv tool install), run:

~/.local/share/uv/tools/substack-saved-mcp/bin/playwright install

If you are using a local development environment (via uv sync), run:

uv run playwright install

I edited the source code, but the installed substack-saved-mcp command still behaves like the old version. Why?

uv tool install copies the package into its own isolated environment at install time — it does not track your working tree. If you edited files under src/ (or pulled new commits) after installing the tool system-wide, the globally installed copy is stale and keeps running the old code, even though uv run substack-saved-mcp ... from the repo would use the latest source.

Reinstall from your current working tree to pick up the changes:

uv tool install . --no-cache --force

• --force replaces the existing installed version instead of skipping the install because a version is already present.

• --no-cache ensures a fresh build rather than reusing a cached wheel/build artifact from before your edits.

Do this any time after modifying the codebase and before relying on the globally installed substack-saved-mcp binary (as opposed to uv run substack-saved-mcp, which always reflects the working tree).