Parinfer MCP Server

An MCP (Model Context Protocol) server that uses the parinfer-rust library to automatically fix parentheses and brackets in Clojure code based on indentation.

Purpose

This server is designed to help LLMs correct Clojure code when parentheses are mismatched or incorrectly nested. It takes Clojure code with correct indentation but potentially incorrect parentheses/brackets and outputs corrected code.

Building

make build

The binary will be available at target/release/parinfer-mcp-server.

Usage

The MCP server can be used with any MCP-compatible client (like Claude Desktop, Cline, etc.).

Configuration

Add to your MCP client configuration:

Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json on macOS):

{
  "mcpServers": {
    "parinfer": {
      "command": "/absolute/path/to/parinfer-mcp/target/release/parinfer-mcp-server"
    }
  }
}

For other platforms and clients, see MCP_USAGE.md.

Available Tools

The MCP server provides one tool:

• fix_parens: Fixes mismatched or missing closing parentheses in Clojure code based on indentation
  • Input: code (string) - Clojure code with correct indentation
  • Output: Corrected Clojure code with proper parentheses

How It Works

The server uses parinfer's "indent mode" which:

1. Preserves all indentation exactly as provided
2. Infers correct closing parentheses/brackets based on indentation
3. Fixes mismatched or missing closing delimiters

Testing

Run tests:

make test

Test with MCP Inspector:

npx @modelcontextprotocol/inspector ./target/release/parinfer-mcp-server

See MCP_USAGE.md for detailed testing instructions.

Example

Input with incorrect parentheses:

(defn nnbsp [n
  (apply str (repeat n nbsp))

Output with corrected parentheses:

(defn nnbsp [n]
  (apply str (repeat n nbsp)))