Safe shell argument escaping for bash/cmd/PowerShell via @mukundakatta/shellquote-mcp (npx) — 4 tools, prevents command injection

Recipe: Safe shell argument escaping via @mukundakatta/shellquote-mcp

Install & launch

npm install @mukundakatta/shellquote-mcp
# Server binary: node_modules/.bin/shellquote-mcp
# Or via npx: npx @mukundakatta/shellquote-mcp
# Transport: stdio, MCP JSON-RPC

4 Tools

Trace 1 — Bash: command injection neutralized

→ tools/call  quote_bash  { arg: "hello; rm -rf / && echo pwned" }
← {"quoted":"'hello; rm -rf / && echo pwned'"}
  latency: 1ms

The entire string becomes a harmless single-quoted literal — ;, &&, and all metacharacters are suppressed.

Trace 2 — Bash argv: multi-arg with apostrophes and $variables

→ tools/call  quote_bash_argv  { args: ["grep", "-r", "it's a match", "$HOME/docs", "file with spaces.txt"] }
← {"command":"grep -r 'it'\\''s a match' '$HOME/docs' 'file with spaces.txt'"}
  latency: 0ms

The apostrophe in "it's" is handled with the '\'' escape-out-of-single-quote technique. $HOME is suppressed (no expansion).

Trace 3 — Bash: $variable and subshell suppression

→ tools/call  quote_bash  { arg: "$HOME/.config/$(whoami)" }
← {"quoted":"'$HOME/.config/$(whoami)'"}
  latency: 0ms

Trace 4 — PowerShell quoting

→ tools/call  quote_powershell  { arg: "C:\\Users\\John's Files\\report (final).docx" }
← {"quoted":"'C:\\Users\\John''s Files\\report (final).docx'"}
  latency: 0ms

PowerShell single-quotes double the embedded ' — correct PS escaping.

Trace 5 — cmd.exe quoting

→ tools/call  quote_cmd  { arg: "dir \"hello\" & del important.txt" }
← {"quoted":"\"dir \"\"hello\"\" & del important.txt\""}
  latency: 1ms

Note: cmd.exe has unfixable corner cases with ^, !, %. Prefer PowerShell when possible.

Why this matters for agents

Any agent that composes shell commands from dynamic input (file paths from users, search terms, LLM-generated strings) risks command injection if arguments aren't properly escaped. This server is a zero-dependency safety primitive: pass the raw argument, get back a safely quoted string, compose into the command. Sub-millisecond, no network calls.