Regex Explainer MCP server

• explain_regexFree

  Explain a regular expression in plain English and detect the failure modes that make patterns dangerous rather than merely wrong. Use this whenever a regex needs to be read, reviewed, or verified — and ALWAYS before putting a pattern somewhere it will run against untrusted input. The critical check is catastrophic backtracking: a pattern like (a+)+$ is three characters longer than a safe equivalent, looks harmless, and takes minutes of CPU on a 30-character input that almost matches. That makes it a denial-of-service vector. Whether a pattern is vulnerable depends on whether nested quantifiers can match the same characters in more than one way, which is a structural property that is unreliable to judge by reading. It also flags: missing anchors (an unanchored validator accepts any string that merely CONTAINS a valid value), unescaped dots, character ranges like [A-z] that span punctuation, alternation precedence mistakes where an anchor applies to only one branch, and constructs JavaScript does not support. Input: `pattern` accepts either a bare pattern or a full /pattern/flags literal. JavaScript syntax; PCRE-only constructs are reported as unsupported rather than guessed at. Returns: `summary` (one sentence), `steps` (an ordered walkthrough), `warnings` (each with a code, severity, detail, and fix), `flagNotes`, capture group counts and names, and `hasBlockingIssue` — check that flag first. If the pattern cannot be parsed it returns an error naming the position, rather than a plausible-looking explanation of something else.

• –Code scanremote-only server, no package to scann/a
• Live reliabilityremote reachable in 1447ms20/20
• Tool poisoning1 tool descriptions checked15/15
• Auth qualityopen endpoint, read-only tools10/15
• Maintenancerepository not readable: repo not found3/15
• Maintainer identityverified namespace with website, no repo4/10

Regex Explainer: common questions

Is Regex Explainer MCP server safe?

With care: it is graded C, so read the findings first (69/100). Read the Regex Explainer safety report

How do I install Regex Explainer?

It runs remotely at regex-explainer.gumballtools.com. Add it to Claude Code, Claude Desktop or Cursor with the snippets above, or call it through the mcp.market gateway without installing anything.

Does Regex Explainer need an API key?

Not as far as the registry entry and our scan can tell: no credentials are declared or required.

Is Regex Explainer maintained?

The latest release is v0.1.0.

Is Regex Explainer up?

100% of our last 6 checks got an answer. We check remote servers about four times a day.