What is the key difference between Inbox Zero and FlowCastle?

Inbox Zero belongs to the Communication category with local stdio execution, while FlowCastle belongs to the Communication category with cloud HTTP/SSE execution.

How do I install Inbox Zero or FlowCastle in Claude Desktop or Cursor?

Copy the mcpServers JSON configuration snippet provided on this page into your claude_desktop_config.json or ~/.cursor/mcp.json file and restart your AI client.

Are Inbox Zero and FlowCastle free or paid?

Inbox Zero operates under a Freemium model (OAuth 2.0). FlowCastle operates under a Free / Open Source model (No auth required).

Which MCP server has more tools and community activity?

Inbox Zero lists 6 tools with 1 views and 11,923 GitHub stars. FlowCastle lists 0 tools with 0 views and 2 GitHub stars.

Can I use both Inbox Zero and FlowCastle together in the same MCP host?

Yes! MCP hosts like Claude Desktop, Cursor, Windsurf, Cline, and VS Code support configuring multiple servers under the mcpServers object simultaneously.

How do I install Inbox Zero or FlowCastle in Claude Desktop, Cursor, or Windsurf?

Both servers follow the standard Model Context Protocol configuration format. Simply copy the JSON block from the configuration section above and paste it into your AI client's mcpServers configuration object (for instance in claude_desktop_config.json or ~/.cursor/mcp.json ), then completely restart or refresh the application.

Are Inbox Zero and FlowCastle free to use, or do they require API keys?

Inbox Zero is listed under a Freemium model with OAuth 2.0 . FlowCastle operates under a Free / Open Source model with No auth required . If environment variables are required (such as API keys), be sure to define them under the env key in your MCP client's configuration file.

Can I run both Inbox Zero and FlowCastle at the same time in my AI client?

Yes! MCP clients support multi-server orchestration. You can include both elie222-inbox-zero and flowcastle as distinct keys inside the single mcpServers object in your configuration file. Your AI assistant will automatically select and call the appropriate tool from either server during chat sessions.

Which MCP server has higher directory engagement and quality ratings?

On AllMCPs, Inbox Zero has a Quality Score of 57 /100 ( Good ) with 1 views, 0 installs, and 11,923 GitHub stars. FlowCastle holds a Quality Score of 41 /100 ( Fair ) with 0 views, 0 installs, and 2 GitHub stars.

Side-by-Side Model Context Protocol Comparison

Inbox Zero vs FlowCastle

In-depth architectural comparison of the Inbox Zero and FlowCastle MCP servers. Compare execution transports, security boundaries, tool capabilities, quality scores, and ready-to-paste client installation snippets for Claude, Cursor, Windsurf, and VS Code.

At a Glance & Executive Verdict

Inbox Zero

Communication · Local stdio

Quality: 57/100 (Good) | Auth: OAuth 2.0

FlowCastle

Communication · Remote HTTP/SSE

Quality: 41/100 (Fair) | Auth: No auth required

Verdict Summary: Choose Inbox Zero if you need specialized Communication tools running via a local process. Choose FlowCastle if your workspace requires Communication integration with remote web transport. Both servers can be configured concurrently in your client's mcpServers manifest.

Which MCP Server Should You Choose?

Choose Inbox Zero when:

You need dedicated capabilities in the Communication domain.
You prefer local stdio subprocess transport architecture.
Your security boundary fits: OAuth 2.0 (Freemium).
You have access to required keys: GOOGLE_CLIENT_ID, GOOGLE_CLIENT_SECRET, MICROSOFT_CLIENT_ID, MICROSOFT_CLIENT_SECRET, GOOGLE_BASE_URL, MICROSOFT_BASE_URL.
Primary tools included: AI personal assistant for inbox organization and reply drafting, Natural language AI rules for custom email handling, Reply Zero tracking for reply and follow-up management.

Explore Inbox Zero Details

Choose FlowCastle when:

You need dedicated capabilities in the Communication domain.
You prefer remote streaming HTTP/SSE transport architecture.
Your security boundary fits: No auth required (Free / Open Source).

Explore FlowCastle Details

Feature & Specification Comparison

Specification	Inbox Zero elie222 Communication	FlowCastle Communication
Summary	An MCP server for Inbox Zero. Adds functionality on top of Gmail like finding out which emails you need to reply to or need to follow up on.	Build, edit, and deploy Telegram bots on FlowCastle's hosted visual flow platform.
Category & Scope	Communication	Communication

Tools & Capabilities Breakdown

Inbox Zero Tools (6)

AI personal assistant for inbox organization and reply drafting

Natural language AI rules for custom email handling

Reply Zero tracking for reply and follow-up management

Bulk unsubscriber and archiver tools

Smart filing of attachments to Google Drive or OneDrive

Slack and Telegram integration for chat-based inbox control

FlowCastle Tools (0)

No explicit tool names declared in metadata yet. Check project README on main listing page.

Ready-to-Paste Client Configurations

Paste either (or both) of these JSON server blocks into your client config file (e.g. claude_desktop_config.json or ~/.cursor/mcp.json).

Inbox Zero Configuration

mcpServers (Claude Desktop / Cursor)

{
  "mcpServers": {
    "elie222-inbox-zero": {
      "command": "npx",
      "args": [
        "-y",
        "@inbox-zero/cli"
      ],
      "env": {
        "GOOGLE_CLIENT_ID": "YOUR_GOOGLE_CLIENT_ID_HERE",
        "GOOGLE_CLIENT_SECRET": "YOUR_GOOGLE_CLIENT_SECRET_HERE",
        "MICROSOFT_CLIENT_ID": "YOUR_MICROSOFT_CLIENT_ID_HERE",
        "MICROSOFT_CLIENT_SECRET": "YOUR_MICROSOFT_CLIENT_SECRET_HERE",
        "GOOGLE_BASE_URL": "YOUR_GOOGLE_BASE_URL_HERE",
        "MICROSOFT_BASE_URL": "YOUR_MICROSOFT_BASE_URL_HERE"
      }
    }
  }
}

FlowCastle Configuration

mcpServers (Claude Desktop / Cursor)

{
  "mcpServers": {
    "flowcastle": {
      "url": "https://flowcastle.ai"
    }
  }
}

Frequently Asked Questions

Inbox Zero is categorized under Communication and uses a local stdio subprocess. In contrast, FlowCastle belongs to Communication using remote streaming HTTP/SSE transport. Select Inbox Zero when you need capabilities focused on communication and FlowCastle when you require tools for communication.

More alternatives to Inbox Zero More alternatives to FlowCastle Communication category hub