Regex Explainer
Explain any regular expression, and catch the ones that can hang.
Why delegate this
Whether a pattern backtracks catastrophically depends on nested quantifier structure that is unreliable to eyeball — and getting it wrong ships a denial-of-service vector in a validator.
Tools
regex_explain
Explain a regex and check it for ReDoS
Explain a regular expression in plain English and detect catastrophic backtracking. ALWAYS call this before putting a pattern where it will run against untrusted input: (a+)+$ looks harmless and takes minutes of CPU on a failing 30-character input. Also flags missing anchors, unescaped dots, ranges like [A-z] that span punctuation, and alternation precedence mistakes. Check hasBlockingIssue first.
Direct endpoint:
https://regex-explainer-omega.vercel.app/api/v1/explain
Two ways to call it
Through the aggregator, which gives you every other tool at the same time:
claude mcp add --transport http gumball https://gumballtools.com/api/mcpOr directly, if this is the only capability you want:
claude mcp add --transport http regex-explainer https://regex-explainer-omega.vercel.app/api/mcp