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Connection Types for MCP Servers

MCP servers can communicate with clients using different connection protocols, each with its own advantages and use cases. This guide explains the primary connection types supported by mcp_use:

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Standard Input/Output (STDIO)

STDIO connections run the MCP server as a child process and communicate through standard input and output streams.

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Characteristics:

  • Local Operation: The server runs as a child process on the same machine
  • Simplicity: Easy to set up with minimal configuration
  • Security: No network exposure, ideal for sensitive operations
  • Performance: Low latency for local operations

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Configuration Example:

{
  "mcpServers": {
    "stdio_server": {
      "command": "npx",
      "args": ["@my-mcp/server"],
      "env": {}
    }
  }
}

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HTTP Connections

HTTP connections communicate with MCP servers over standard HTTP/HTTPS protocols.

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Characteristics:

  • RESTful Architecture: Follows familiar HTTP request/response patterns
  • Statelessness: Each request is independent
  • Compatibility: Works well with existing web infrastructure
  • Firewall-Friendly: Uses standard ports that are typically open

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Configuration Example:

{
  "mcpServers": {
    "http_server": {
      "url": "http://localhost:3000",
      "headers": {
        "Authorization": "Bearer ${AUTH_TOKEN}"
      }
    }
  }
}

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Sandboxed Execution

Sandboxed execution runs STDIO-based MCP servers in a cloud sandbox environment using E2B, rather than locally on your machine.

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Installation

To use sandboxed execution, you need to install the E2B dependency: 
# Install mcp-use with E2B support
pip install "mcp-use[e2b]"

# Or install the dependency directly
pip install e2b-code-interpreter
You’ll also need an E2B API key. You can sign up at e2b.dev to get your API key.

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Characteristics:

  • Cloud Execution: The server runs in a secure cloud environment
  • No Local Dependencies: No need to install server dependencies locally
  • Consistent Environment: Same environment regardless of local setup
  • Resource Isolation: Server operations won’t impact local system resources
  • Secure Execution: Sandbox provides isolation for security-sensitive operations

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Configuration Example:

from mcp_use import MCPClient
from mcp_use.types.sandbox import SandboxOptions

# Define sandbox options
sandbox_options: SandboxOptions = {
    "api_key": "your_e2b_api_key",  # Or use E2B_API_KEY environment variable
    "sandbox_template_id": "code-interpreter-v1"
}

# Create client with sandboxed execution enabled
client = MCPClient.from_dict(
    {
        "mcpServers": {
            "sandboxed_server": {
                "command": "npx",
                "args": ["@my-mcp/server"],
                "env": {}
            }
        }
    },
    sandbox=True,
    sandbox_options=sandbox_options
)

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Choosing the Right Connection Type

The choice of connection type depends on your specific use case:
  1. STDIO: Best for local development, testing, and enhanced security scenarios where network exposure is a concern
  2. HTTP: Ideal for stateless operations, simple integrations, and when working with existing HTTP infrastructure
  3. Sandboxed: Best when you need to run MCP servers without installing their dependencies locally, or when you want consistent execution environments across different systems
When configuring your mcp_use environment, you can specify the connection type in your configuration file as shown in the examples above.

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Using Connection Types

Connection types are automatically inferred from your configuration file based on the parameters provided: 
from mcp_use import MCPClient

# The connection type is automatically inferred based on your config file
client = MCPClient.from_config_file("config.json", server_name="my_server")

client = MCPClient.from_config_file(
    "config.json",
    options=client_options
)
For example:
  • If your configuration includes command and args and sandbox parameter is False` (default), a local STDIO connection will be used
  • If your configuration includes command and args and sandbox parameter is True`, a sandboxed execution connection will be used
  • If your configuration has a url starting with http:// or https://, an HTTP connection will be used
This automatic inference simplifies the configuration process and ensures the appropriate connection type is used without requiring explicit specification. For more details on connection configuration, see the Configuration Guide.