Plumbkit

by plumbkit.dev · remote · no sign-in to list tools · v1.0.0 · published by dev.plumbkit

Exact utilities for agents: time zones, date math, business days, calculator, units, validation.

Final · 1Changes · 7

Compare Registry entry

16 tools: 1 do something that can't be undone, 7 change things and 8 only read.

Scanned Oct 21, 2026

Deletes or cancels0Claude Code: deny
Can't be undone1Claude Code: ask: see these tools
Changes things7Claude Code: ask: see these tools
Only reads8Claude Code: allow: see these tools

6 checks matched something in the tool definitions. No finding is not a safety guarantee. How the checks work.

claude mcp add --transport http plumbkit https://plumbkit.dev/mcp

Findings

Matches of fixed checks, with the text they matched.

5 warn1 info

Warnconvert_timezone
The server marks "convert_timezone" read-only (readOnlyHint: true), and its own name, description or input give the class "write".
Matched text
annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The name "convert_timezone" says "convert": a word for a change.
What this check looks for
Warndate_add
The server marks "date_add" read-only (readOnlyHint: true), and its own name, description or input give the class "write".
Matched text
annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The name "date_add" says "add": a word for a change.
What this check looks for
Warncalculate
The server marks "calculate" read-only (readOnlyHint: true), and its own name, description or input give the class "write".
Matched text
annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The description's first verb is "evaluate": a word for a change.
What this check looks for
Warnconvert_units
The server marks "convert_units" read-only (readOnlyHint: true), and its own name, description or input give the class "irreversible".
Matched text
annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The name "convert_units" says "convert": a word for a change.
What this check looks for
Warnregex_test
The server marks "regex_test" read-only (readOnlyHint: true), and its own name, description or input give the class "write".
Matched text
annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The description's first verb is "run": a word for a change.
What this check looks for
Infovalidate_url
The description mentions "credentials".
Matched text
description: "...scheme, private/localhost addresses and credentials embedded in the URL. Does not fetch the..."
What this check looks for

Tools

Open a tool for its reasons and full description. Descriptions are the publisher's own words, shown as they are.

16 tools

Can't be undone 1Sends, pays, publishes or merges: once done, it cannot be taken back.Claude Code: ask

convert_unitsConverts a value between units of length, mass, volume (US and imperial), area, speed, time, digital data (KB vs KiB, bits vs bytes), energy, pressure and temperature.1 finding
Why it is in this group
- The name "convert_units" says "convert": a word for a change.
- The input addresses people (input.to): what it sends cannot be taken back.
- The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
Findings
- Warn
  The server marks "convert_units" read-only (readOnlyHint: true), and its own name, description or input give the class "irreversible".
  Matched text
  annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The name "convert_units" says "convert": a word for a change.
  What this check looks for
Description, as the server wrote it
Converts a value between units of length, mass, volume (US and imperial), area, speed, time, digital data (KB vs KiB, bits vs bytes), energy, pressure and temperature. Accepts common abbreviations (km, lb, fl oz, mph, °F, GiB). US customary units are used for cup/pint/quart/gallon unless you say imperial.
Annotations the server declares
- title: Unit converter
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false

Changes things 7Creates or changes something that can be changed back.Claude Code: ask

business_daysWorks with business (working) days.No findings
Why it is in this group
- Nothing in its name or description says what it does, so it is counted as a write.
- The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
Description, as the server wrote it
Works with business (working) days. mode "add": returns the date N business days after start_date (start_date itself is not counted; negative N goes backward; 0 returns start_date, or the next business day if start_date is not one). mode "count": counts business days from start_date to end_date, including both ends. Weekends default to Saturday and Sunday. Public holidays are NOT built in — pass them in "holidays".
Annotations the server declares
- title: Business day calculator
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false
calculateEvaluates an arithmetic expression exactly, so you don't have to do mental math.1 finding
Why it is in this group
- The description's first verb is "evaluate": a word for a change.
- The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
Findings
- Warn
  The server marks "calculate" read-only (readOnlyHint: true), and its own name, description or input give the class "write".
  Matched text
  annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The description's first verb is "evaluate": a word for a change.
  What this check looks for
Description, as the server wrote it
Evaluates an arithmetic expression exactly, so you don't have to do mental math. Supports + - * / % ^ (or **), parentheses, constants pi/e/tau and functions: sqrt, cbrt, abs, round(x, digits), floor, ceil, trunc, sign, ln, log(x[, base]), log10, log2, exp, pow, sin, cos, tan, asin, acos, atan, atan2, min, max, hypot, factorial. Trig uses radians. Example: "(1250 * 1.08^5) - 1250".
Annotations the server declares
- title: Exact calculator
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false
convert_timezoneConverts a date/time from one time zone to another, correctly handling daylight saving time.1 finding
Why it is in this group
- The name "convert_timezone" says "convert": a word for a change.
- The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
Findings
- Warn
  The server marks "convert_timezone" read-only (readOnlyHint: true), and its own name, description or input give the class "write".
  Matched text
  annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The name "convert_timezone" says "convert": a word for a change.
  What this check looks for
Description, as the server wrote it
Converts a date/time from one time zone to another, correctly handling daylight saving time. If the input already includes an offset or 'Z', from_timezone is ignored.
Annotations the server declares
- title: Convert time zones
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false
date_addAdds or subtracts a duration (years, months, weeks, days, hours, minutes, seconds) to a date/time.1 finding
Why it is in this group
- The name "date_add" says "add": a word for a change.
- The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
Findings
- Warn
  The server marks "date_add" read-only (readOnlyHint: true), and its own name, description or input give the class "write".
  Matched text
  annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The name "date_add" says "add": a word for a change.
  What this check looks for
Description, as the server wrote it
Adds or subtracts a duration (years, months, weeks, days, hours, minutes, seconds) to a date/time. Use negative numbers to subtract. Calendar-aware: adding 1 month to Jan 31 gives Feb 28/29, and adding days keeps the same local clock time across daylight-saving changes.
Annotations the server declares
- title: Add or subtract time
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false
hash_textComputes a cryptographic hash (SHA-1, SHA-256, SHA-384, SHA-512) of text, or encodes/decodes it as Base64, Base64URL, hex or URL-encoding.No findings
Why it is in this group
- Nothing in its name or description says what it does, so it is counted as a write.
- The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
Description, as the server wrote it
Computes a cryptographic hash (SHA-1, SHA-256, SHA-384, SHA-512) of text, or encodes/decodes it as Base64, Base64URL, hex or URL-encoding. Text is treated as UTF-8.
Annotations the server declares
- title: Hash and encode text
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false
json_repairTurns almost-JSON into valid JSON: removes markdown code fences, comments and trailing commas, adds missing quotes, commas and closing brackets, converts single quotes, Python True…No findings
Why it is in this group
- Nothing in its name or description says what it does, so it is counted as a write.
- The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
Description, as the server wrote it
Turns almost-JSON into valid JSON: removes markdown code fences, comments and trailing commas, adds missing quotes, commas and closing brackets, converts single quotes, Python True/False/None and truncated output. Returns the repaired JSON string and whether the input was already valid.
Annotations the server declares
- title: Fix broken JSON
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false
regex_testRuns a JavaScript regular expression against text and returns every match with its position and capture groups, or the text after replacement.1 finding
Why it is in this group
- The description's first verb is "run": a word for a change.
- The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
Findings
- Warn
  The server marks "regex_test" read-only (readOnlyHint: true), and its own name, description or input give the class "write".
  Matched text
  annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The description's first verb is "run": a word for a change.
  What this check looks for
Description, as the server wrote it
Runs a JavaScript regular expression against text and returns every match with its position and capture groups, or the text after replacement. Use it to verify a regex actually works before relying on it.
Annotations the server declares
- title: Test a regular expression
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false

Only reads 8Looks things up and changes nothing.Claude Code: allow

current_timeReturns the exact current date, time, weekday and UTC offset in any time zone.No findings
Why it is in this group
- The description's first verb is "return": a word for reading.
Description, as the server wrote it
Returns the exact current date, time, weekday and UTC offset in any time zone. Use this whenever you need to know today's date or the current time instead of guessing — your training data does not know what day it is.
Annotations the server declares
- title: Current date and time
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: false
- openWorldHint: false
date_diffCalculates the exact time between two dates/times: a calendar breakdown (years, months, days, hours, minutes, seconds) plus totals in days, hours, minutes and seconds, and the numb…No findings
Why it is in this group
- The name "date_diff" says "diff": a word for reading.
Description, as the server wrote it
Calculates the exact time between two dates/times: a calendar breakdown (years, months, days, hours, minutes, seconds) plus totals in days, hours, minutes and seconds, and the number of calendar days. Negative if end is before start.
Annotations the server declares
- title: Time between two dates
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false
json_schema_validateChecks a JSON value against a JSON Schema (drafts 4, 7, 2019-09 and 2020-12) and lists every violation with its location.No findings
Why it is in this group
- The name "json_schema_validate" says "validate": a word for reading.
Description, as the server wrote it
Checks a JSON value against a JSON Schema (drafts 4, 7, 2019-09 and 2020-12) and lists every violation with its location. Use it to confirm structured output or an API payload is correct before sending it. `data` and `schema` may be JSON values or JSON strings.
Annotations the server declares
- title: Validate JSON against a schema
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false
text_statsCounts exactly what language models are bad at counting: characters (as humans see them), words, lines, sentences, paragraphs, UTF-8 bytes, and occurrences of a letter or substring…No findings
Why it is in this group
- The description's first verb is "count": a word for reading.
Description, as the server wrote it
Counts exactly what language models are bad at counting: characters (as humans see them), words, lines, sentences, paragraphs, UTF-8 bytes, and occurrences of a letter or substring (e.g. how many "r" in "strawberry"). Use it to check length limits (tweets, SMS, meta descriptions, form fields) before submitting text.
Annotations the server declares
- title: Count characters, words and lines
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false
validate_emailChecks whether an email address is correctly formatted and returns a normalized version.No findings
Why it is in this group
- The name "validate_email" says "validate": a word for reading.
Description, as the server wrote it
Checks whether an email address is correctly formatted and returns a normalized version. Set check_dns=true to also confirm the domain exists and can receive mail (MX records). Does not send email and cannot confirm that a specific mailbox exists.
Annotations the server declares
- title: Validate an email address
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: true
validate_ibanValidates an International Bank Account Number: country, length for that country, and the mod-97 check digits.No findings
Why it is in this group
- The name "validate_iban" says "validate": a word for reading.
Description, as the server wrote it
Validates an International Bank Account Number: country, length for that country, and the mod-97 check digits. Returns electronic and printed formats. A valid IBAN is correctly formed; this does not confirm the account exists.
Annotations the server declares
- title: Validate an IBAN
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false
validate_phoneValidates a phone number using Google's libphonenumber rules and returns it in E.164 (+14155552671), international and national formats, plus the country and line type (mobile, fix…No findings
Why it is in this group
- The name "validate_phone" says "validate": a word for reading.
Description, as the server wrote it
Validates a phone number using Google's libphonenumber rules and returns it in E.164 (+14155552671), international and national formats, plus the country and line type (mobile, fixed line, toll free...). For numbers without a +country code, pass default_country.
Annotations the server declares
- title: Validate and format a phone number
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false
validate_urlChecks that a URL is well-formed, normalizes it (lowercase host, punycode, default ports removed, spaces encoded) and splits it into parts including each query parameter.1 finding
Why it is in this group
- The name "validate_url" says "validate": a word for reading.
Findings
- Info
  The description mentions "credentials".
  Matched text
  description: "...scheme, private/localhost addresses and credentials embedded in the URL. Does not fetch the..."
  What this check looks for
Description, as the server wrote it
Checks that a URL is well-formed, normalizes it (lowercase host, punycode, default ports removed, spaces encoded) and splits it into parts including each query parameter. Flags common problems such as missing scheme, private/localhost addresses and credentials embedded in the URL. Does not fetch the URL.
Annotations the server declares
- title: Validate and normalize a URL
- readOnlyHint: true
- destructiveHint: false
- idempotentHint: true
- openWorldHint: false

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Install

Pinned to version 1.0.0. Values in angle brackets are yours to fill in.

claude mcp add --transport http plumbkit https://plumbkit.dev/mcp

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json

{
  "permissions": {
    "allow": [
      "mcp__plumbkit__current_time",
      "mcp__plumbkit__date_diff",
      "mcp__plumbkit__text_stats",
      "mcp__plumbkit__validate_email",
      "mcp__plumbkit__validate_phone",
      "mcp__plumbkit__validate_url",
      "mcp__plumbkit__validate_iban",
      "mcp__plumbkit__json_schema_validate"
    ],
    "ask": [
      "mcp__plumbkit__convert_timezone",
      "mcp__plumbkit__date_add",
      "mcp__plumbkit__business_days",
      "mcp__plumbkit__calculate",
      "mcp__plumbkit__convert_units",
      "mcp__plumbkit__hash_text",
      "mcp__plumbkit__regex_test",
      "mcp__plumbkit__json_repair"
    ],
    "deny": []
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. It assumes the server is installed as plumbkit. Review it before you use it.

Keep track

Get told when this server's tools change: a new tool, a new description, a new class.

https://anlyon.dev/servers/dev.plumbkit/plumbkit/changes.xml

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Source: MCP Registry. Synced Oct 21, 2026, 18:12 UTC.

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