Regex Explainer
REMOTE · REGEX-EXPLAINER.GUMBALLTOOLS.COM · SCANNED SEP 25
Explain a regex in plain English and detect catastrophic backtracking risk.
Available components
How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. How we score → Why this is hard to score →
Endpoint Security63
- The endpoint's TLS certificate is valid, in date, and uses a strong key. View diagnostics → Pass
- Authorisation not fully verified: no authorisation is required to call this server, and 1 tool(s) never declared a destructiveHint. The MCP spec treats an absent hint as destructive by default, so we cannot call this surface safe. See how to fix → View diagnostics → Unverified
- HTTPS is enforced; there's no plaintext access path. View diagnostics → Pass
- The HSTS (Strict-Transport-Security) header is present. View diagnostics → Pass
- DNSSEC check failed: this domain isn't protected by DNSSEC. See how to fix → View diagnostics → Fail
Transport & Reachability100
- Verified streamable-http transport via a live MCP handshake. View diagnostics → Pass
Schema Quality & AI Usability73
- AI-judged instruction clarity (excellent).Pass
- Context-footprint check failed: tool/resource definitions use about 360 tokens (~360/item across 1 items; 1 tools + 0 resources), over budget; trim descriptions and params. See how to fix → Fail
- Usage-examples check failed: none of the tools include examples. See how to fix → Fail
Stability & Change Management67
- Stability observed for 20 of 30 days with no destabilising changes; credit accrues until the full window elapses.Partial
Tool Coverage100
- 100% of tools have a non-trivial description (not blank, and not just the tool's name).Pass
- 100% of tool parameters carry a description.Pass
Tool Safety100
- No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.Pass
- We read all 1 captured tool definition(s), and no name or description among them implies an irreversible operation.Pass
- An AI judge read all 1 captured unit(s) of tool text and found none that tries to manipulate the model reading it.Pass
Capabilities100
- Implements a current MCP spec version (2026-07-28).Pass
How do I install the Regex Explainer MCP server?
Regex Explainer is a hosted endpoint at https://regex-explainer.gumballtools.com/api/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.
remote · regex-explainer.gumballtools.com
claude mcp add --transport http com-gumballtools-regex-explainer 'https://regex-explainer.gumballtools.com/api/mcp'
{
"mcpServers": {
"com-gumballtools-regex-explainer": {
"url": "https://regex-explainer.gumballtools.com/api/mcp"
}
}
} {
"servers": {
"com-gumballtools-regex-explainer": {
"type": "http",
"url": "https://regex-explainer.gumballtools.com/api/mcp"
}
}
} [mcp_servers.com-gumballtools-regex-explainer] url = "https://regex-explainer.gumballtools.com/api/mcp"
{
"$schema": "https://opencode.ai/config.json",
"mcp": {
"com-gumballtools-regex-explainer": {
"type": "remote",
"url": "https://regex-explainer.gumballtools.com/api/mcp",
"enabled": true
}
}
} openclaw mcp add com-gumballtools-regex-explainer --url 'https://regex-explainer.gumballtools.com/api/mcp' --transport streamable-http
mcp_servers:
com-gumballtools-regex-explainer:
url: "https://regex-explainer.gumballtools.com/api/mcp" {
"McpServers": {
"com-gumballtools-regex-explainer": {
"Transport": "http",
"Url": "https://regex-explainer.gumballtools.com/api/mcp"
}
}
} assistant mcp add com-gumballtools-regex-explainer -t streamable-http -u 'https://regex-explainer.gumballtools.com/api/mcp'
{
"mcpServers": {
"com-gumballtools-regex-explainer": {
"type": "http",
"url": "https://regex-explainer.gumballtools.com/api/mcp"
}
}
} The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.
Every change we have recorded for this component, newest first. Security-relevant changes are always shown. ▲ marks a change for the better, ▼ a change for the worse; unmarked changes are neutral.
- 25 Sept 26 +1
- We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
- 23 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 57 to 60. That category is still filling its 30-day observation window: 17 days of observed history at the previous scan, 18 at this one. The score rises as the window fills, whether or not the server changes.
- 21 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 50 to 53. That category is still filling its 30-day observation window: 15 days of observed history at the previous scan, 16 at this one. The score rises as the window fills, whether or not the server changes.
- 19 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 43 to 47. That category is still filling its 30-day observation window: 13 days of observed history at the previous scan, 14 at this one. The score rises as the window fills, whether or not the server changes.
- 16 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 33 to 37. That category is still filling its 30-day observation window: 10 days of observed history at the previous scan, 11 at this one. The score rises as the window fills, whether or not the server changes.
- 14 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 27 to 30. That category is still filling its 30-day observation window: 8 days of observed history at the previous scan, 9 at this one. The score rises as the window fills, whether or not the server changes.
- 12 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 20 to 23. That category is still filling its 30-day observation window: 6 days of observed history at the previous scan, 7 at this one. The score rises as the window fills, whether or not the server changes.
- 10 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 13 to 17. That category is still filling its 30-day observation window: 4 days of observed history at the previous scan, 5 at this one. The score rises as the window fills, whether or not the server changes.
Diagnostic detail from the automated scan of this channel: what the scanner observed at each step, so you can see exactly where a check passed or failed. It is informational only and never changes the trust score.
Captured 25 Sept 2026 · Probed https://regex-explainer.gumballtools.com/api/mcp
TLS valid
Negotiated TLS 1.3 with TLS_AES_128_GCM_SHA256 .
| Subject | Issuer | Valid from | Valid until | Key | Signature | Serial |
|---|---|---|---|---|---|---|
| CN=*.gumballtools.com | CN=YR2,O=Let's Encrypt,C=US | 6 Sept 2026 | 5 Dec 2026 | RSA 2048 | SHA256-RSA | 60927985e79d22e7a1106139f609d74b0e4 |
| SANs: *.gumballtools.com, gumballtools.com | ||||||
| CN=YR2,O=Let's Encrypt,C=US (CA) | CN=Root YR,O=ISRG,C=US | 3 Sept 2025 | 2 Sept 2028 | RSA 2048 | SHA256-RSA | 4ebd24947e24d394802d84a52fd5b319 |
| CN=Root YR,O=ISRG,C=US (CA) | CN=ISRG Root X1,O=Internet Security Research Group,C=US | 13 May 2026 | 2 Sept 2032 | RSA 4096 | SHA256-RSA | f24b6d17f9d9ad7cb1c9fea78782699f |
Background: What to check on a remote MCP endpoint →
DNSSEC insecure
Validation of regex-explainer.gumballtools.com. — Not signed
| Zone | DS | Keys | Algorithms | Outcome |
|---|---|---|---|---|
| . | trust_anchor | 20326, 38696 | 8, 8 | Verified |
| com. | present | 19718 | 13 | Verified |
| gumballtools.com. | absent | Unsigned (proven) parent-signed NSEC/NSEC3 proves an unsigned delegation |
Authentication No authorisation required
The endpoint answered without asking for a token. Anyone who knows the URL can reach it.
| Result | No authorisation required |
|---|---|
| HTTP status | 200 |
| Header | Value |
|---|---|
| strict-transport-security | max-age=63072000 |
Background: How OAuth 2.1 works in the 2026 MCP spec →
Transports 2 probes
| Transport | URL | Outcome | Status | Location |
|---|---|---|---|---|
| streamable-http | https://regex-explainer.gumballtools.com/api/mcp | Verified | 200 | |
| http (plaintext) | http://regex-explainer.gumballtools.com/api/mcp | HTTPS enforced | 308 | https://regex-explainer.gumballtools.com/api/mcp |
The tools this component advertises to a client, with an estimated token cost for each. Expand a tool to see its parameters and schema. The per-tool counts are indicative and are not scored directly; the schema's total context footprint is one signal in Schema Quality & AI Usability. A tool's description is untrusted text the model reads on every call, which is what makes this list a security surface and not just an inventory: how tool poisoning works →
explain_regex Explain a regular expression ~360
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.
| Name | Type | Req | Description |
|---|---|---|---|
| pattern | string | yes | A JavaScript regular expression, either bare ("^\d+$") or as a full literal ("/^\d+$/gi"). Up to 2000 characters. |
No output schema declared.
No examples provided.
What is the Regex Explainer MCP server?
Regex Explainer is an MCP server listed in the public MCP registry as com.gumballtools/regex-explainer. Explain a regex in plain English and detect catastrophic backtracking risk. This page covers its hosted endpoint (https://regex-explainer.gumballtools.com/api/mcp).
Is the Regex Explainer MCP server safe to use?
Regex Explainer scores 76 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.
What tools does the Regex Explainer MCP server expose?
Regex Explainer exposes 1 tool: explain_regex. Their descriptions and schemas cost roughly 360 tokens of context every time the server is loaded.
Does the Regex Explainer MCP server require authentication?
No. We connected to Regex Explainer without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.
Is the Regex Explainer MCP server still maintained?
Regex Explainer is still listed as active in the MCP registry. We last reached this channel on 25 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.