Superargs MCP Server

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