What is the key difference between FlowCastle and ARBuilder?

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

How do I install FlowCastle or ARBuilder 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 FlowCastle and ARBuilder free or paid?

FlowCastle operates under a Free / Open Source model (No auth required). ARBuilder operates under a Freemium model (API Key required).

Which MCP server has more tools and community activity?

FlowCastle lists 0 tools with 1 views and 2 GitHub stars. ARBuilder lists 19 tools with 2 views and 24 GitHub stars.

Can I use both FlowCastle and ARBuilder 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.

Side-by-Side Model Context Protocol Comparison

FlowCastle vs ARBuilder

In-depth architectural comparison of the FlowCastle and ARBuilder 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

FlowCastle

Communication · Remote HTTP/SSE

Quality: 39/100 (Fair) | Auth: No auth required

ARBuilder

Communication · Local stdio

Quality: 56/100 (Good) | Auth: API Key required

Verdict Summary: Choose FlowCastle if you need specialized Communication tools running via a hosted cloud SSE transport. Choose ARBuilder if your workspace requires Communication integration with local subprocess execution. Both servers can be configured concurrently in your client's mcpServers manifest.

Which MCP Server Should You Choose?

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

Choose ARBuilder when:

You need dedicated capabilities in the Communication domain.
You prefer local stdio subprocess transport architecture.
Your security boundary fits: API Key required (Freemium).
You have access to required keys: ARBUILDER_API_KEY.
Primary tools included: get_stylus_context, generate_stylus_code, ask_stylus.

Explore ARBuilder Details

Feature & Specification Comparison

Specification	FlowCastle Communication	ARBuilder Quantum3-Labs Communication
Summary	Build, edit, and deploy Telegram bots on FlowCastle's hosted visual flow platform.	AI-powered code generator for the Arbitrum ecosystem. 19 MCP tools for Stylus smart contracts, SDK bridging, full-stack dApps, and Orbit chain deployment, backed by RAG-based retrieval over Arbitrum documentation.
Category & Scope	Communication

Tools & Capabilities Breakdown

FlowCastle Tools (0)

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

ARBuilder Tools (19)

get_stylus_context

RAG retrieval for docs and code examples

generate_stylus_code

Generate Stylus contracts from prompts

ask_stylus

Q&A, debugging, concept explanations

generate_tests

Generate unit/integration/fuzz tests

get_workflow

Build/deploy/test workflow guidance

validate_stylus_code

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).

FlowCastle Configuration

mcpServers (Claude Desktop / Cursor)

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

ARBuilder Configuration

mcpServers (Claude Desktop / Cursor)

{
  "mcpServers": {
    "quantum3-labs-arbuilder": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-remote"
      ],
      "env": {
        "ARBUILDER_API_KEY": "YOUR_ARBUILDER_API_KEY_HERE"
      }
    }
  }
}

Frequently Asked Questions

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

More alternatives to FlowCastle More alternatives to ARBuilder Communication category hub