Superargs

What is Superargs?

Superargs is a middleware wrapper for MCP servers that allows setting up MCP server arguments during runtime instead of during initial setup. It acts as a proxy that forwards all MCP requests (tools, prompts, resources, messages, roots) to a child server and introduces an additional tool to manage those arguments. It is supported by Superinterface, Supermachine, and Supercorp.

How to use Superargs?

Run Superargs via npx with the --stdio flag and a shell command containing placeholders in the form {{argName}}. For example: npx -y superargs --stdio "npx -y @modelcontextprotocol/server-postgres {{databaseUrl}}". Optionally set a custom tool name with --update-args-tool-name. At start, if the underlying server can run without arguments, it will provide its tools plus an update_args tool; if it requires arguments to start, only the update_args tool is available until arguments are provided.

Key features of Superargs

• Dynamic arg injection: replace placeholders with runtime values
• Customizable tool name via --update-args-tool-name
• Forwards all MCP requests to the child server
• Sends change notifications when args are updated

Use cases of Superargs

• Provide authentication tokens to a GitHub MCP server on the fly
• Supply database connection strings to a PostgreSQL MCP server during a chat session
• Let end users configure a SQLite database path without admin pre‑configuration
• Securely pass CLI arguments to any stdio MCP server at runtime

FAQ from Superargs

What does Superargs do?

Superargs lets you provide arguments (like tokens or file paths) to any MCP server during your interaction with an AI assistant, instead of during initial server setup.

How do I run Superargs?

Use the command npx -y superargs --stdio "your_mcp_command_with_{{args}}". The {{argName}} placeholders are replaced at runtime using the update_args tool.

What happens if the MCP server requires arguments to start?

If the server requires arguments to start, it will not start until the arguments are set. Until then, only the update_args tool is available; all other MCP functions return empty results or error messages.

How are sensitive arguments handled?

Arguments are passed to the child MCP server in the command string; nothing is stored by Superargs. To prevent the LLM from seeing the arguments, make a direct call to the MCP server through your own code rather than letting the assistant call the tool.

Can I rename the update_args tool?

Yes, use the optional flag --update-args-tool-name to set a custom name. The default name is update_args.