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MCP Discovery Node

MCP Discovery Node Screenshot

Overview​

The Model Context Protocol (MCP) enables communication with MCP-compliant servers through either HTTP or Stdio transports.

The MCP Discovery Node enables the ability to query an MCP servers and fetch Tools or Prompts in the server.

Currently, the MCP Discovery Node currently utilizes the following MCP request methods for a compliant server:

MCP Discovery Node uses the official MCP Typescript SDK (@modelcontextprotocol/sdk) and requires a node executor when running the graph in the Rivet IDE.

The MCP Discovery Node supports two communication modes:

  1. HTTP Mode: Uses Streamable HTTP Transport as default and a SSE Transport as a fallback for server communication.
  2. STDIO Mode: Launches and communicates with local MCP servers using STIDO Transport.

    For STDIO connections with local servers, add the MCP server config in Project > Edit MCP Configuration

Inputs​

TitleData TypeDescriptionDefault ValueNotes
NamestringThe name for the MCP Client instancemcp-clientStandard required parameter for an MCP Client
VersionstringThe version for the MCP Client instance1.0.0Standard required parameter for an MCP Client
Server URL (HTTP)stringThe endpoint URL for the MCP serverNoneOnly available when using HTTP mode with Server URL Input enabled

Configuration​

Setting up MCP Servers (for STDIO mode)​

Add a JSON configuration in your Rivet project: Project > MCP Configuration

Your MCP Configuration is saved and associated with the Rivet project file. All available servers will be list in MCP Nodes.

Example configuration:

{
  "mcpServers": {
    "mongodb": {
      "command": "/path/to/node",
      "args": ["-y", "/path/to/mcp-mongo-server/build/index.js", "mongodb://localhost:27017/your-database"]
    }
  }
}

Example 1: Using HTTP Mode​

  1. Add an MCP Node to your graph
  2. Set "Transport Type" to "HTTP"
  3. Set "Server URL" to your MCP server URL (e.g., http://localhost:8080/mcp)
  4. Make sure enable the Node Executor in Rivet (top-right menu)
  5. Run the graph to see the response from the MCP server

Example 2: Using STDIO Mode with an example​

This example references the example: Weather MCP Server

  1. First, ensure you have set up the Weather MCP server and configured it in your Project > MCP Configuration

Example configuration:

{
  "mcpServers": {
    "weather": {
      "command": "node",
      "args": ["/absolute-path/weather/build/index.js"]
    }
  }
}
  1. Enable the Node Executor in Rivet (top-right menu)
  2. Add an MCP Discovery Node to your graph
  3. Set "Transport Type" to "STDIO"
  4. Set "Server ID" to "weather"
  5. Run the graph to see Tools and Prompts from the server

Error Handling​

The MCP Node provides detailed error handling with specific error types:

  • CONFIG_NOT_FOUND: MCP configuration file not found
  • SERVER_NOT_FOUND: Specified server ID not found in configuration
  • SERVER_COMMUNICATION_FAILED: Failed to communicate with the server
  • INVALID_SCHEMA: Invalid schema for input arguments

Troubleshooting​

STDIO Server Not Found

  • Check your MCP Configuration in your Rivet Project tab
  • Ensure absolute paths in configuration

HTTP Connection Failed

  • Verify server URL
  • Check CORS settings
  • Confirm network connectivity

Node Executor Issues

  • Enable Node executor in Rivet settings
  • Verify Node.js installation
  • Check server executable permissions

FAQ​

Q: Can I use the MCP Node in the browser executor?

A: No. All MCP nodes use the official MCP Node SDK and require the Node Executor to run locally.

Q: How do I handle authentication with MCP servers?

A:

For STDIO mode, authentication details should be included in your server configuration. For HTTP mode, this will be a follow-up feature and not accessible at the moment.

Q: Can I use multiple MCP servers in the same graph?

A: Yes, you can add multiple MCP Nodes, each can be configured to communicate with a different server.

See Also​