Plumbkit

Measured conclusion: Deep-tested. L2 outcome: tools_ok.

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

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Copy this into your MCP client config:

{
  "mcpServers": {
    "Plumbkit": {
      "url": "https://plumbkit.dev/mcp",
      "transport": "streamable-http"
    }
  }
}

Measured tools (16)

• current_time read-only

  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.

  Parameters:

  • timezone — string — IANA time zone name, e.g. "America/New_York", "Europe/London", "Asia/Tokyo", or "UTC". Fixed offsets like "UTC+5:30" also work.

  Hints: read-only yes · destructive no · idempotent no · open-world no

• convert_timezone read-only

  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.

  Parameters:

  • datetime (required) — string — Date/time in ISO 8601 (e.g. "2026-03-08T14:30", "2026-03-08T14:30:00Z", "2026-03-08"), "YYYY-MM-DD HH:mm", a Unix timestamp in seconds or milliseconds, or "now".
  • to_timezone (required) — string — IANA time zone name, e.g. "America/New_York", "Europe/London", "Asia/Tokyo", or "UTC". Fixed offsets like "UTC+5:30" also work.
  • from_timezone — string — IANA time zone name, e.g. "America/New_York", "Europe/London", "Asia/Tokyo", or "UTC". Fixed offsets like "UTC+5:30" also work. Defaults to UTC.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• date_add read-only

  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.

  Parameters:

  • datetime (required) — string — Date/time in ISO 8601 (e.g. "2026-03-08T14:30", "2026-03-08T14:30:00Z", "2026-03-08"), "YYYY-MM-DD HH:mm", a Unix timestamp in seconds or milliseconds, or "now".
  • days — number — days to add (negative to subtract)
  • hours — number — hours to add (negative to subtract)
  • weeks — number — weeks to add (negative to subtract)
  • years — number — years to add (negative to subtract)
  • months — number — months to add (negative to subtract)
  • minutes — number — minutes to add (negative to subtract)
  • seconds — number — seconds to add (negative to subtract)
  • timezone — string — Time zone the arithmetic happens in. IANA time zone name, e.g. "America/New_York", "Europe/London", "Asia/Tokyo", or "UTC". Fixed offsets like "UTC+5:30" also work. Defaults to UTC.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• date_diff read-only

  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.

  Parameters:

  • start (required) — string — Date/time in ISO 8601 (e.g. "2026-03-08T14:30", "2026-03-08T14:30:00Z", "2026-03-08"), "YYYY-MM-DD HH:mm", a Unix timestamp in seconds or milliseconds, or "now".
  • end (required) — string — Date/time in ISO 8601 (e.g. "2026-03-08T14:30", "2026-03-08T14:30:00Z", "2026-03-08"), "YYYY-MM-DD HH:mm", a Unix timestamp in seconds or milliseconds, or "now".
  • timezone — string — Time zone for inputs without an offset. IANA time zone name, e.g. "America/New_York", "Europe/London", "Asia/Tokyo", or "UTC". Fixed offsets like "UTC+5:30" also work. Defaults to UTC.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• business_days read-only

  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".

  Parameters:

  • mode (required) — string — "add" or "count"
  • start_date (required) — string — YYYY-MM-DD
  • days — integer — Business days to add (mode "add")
  • weekend — array — Weekend days as ISO weekday numbers (1=Monday ... 7=Sunday). Default [6, 7]. Example for Friday-Saturday weekends: [5, 6]
  • end_date — string — YYYY-MM-DD (mode "count")
  • holidays — array — Dates (YYYY-MM-DD) to treat as non-working days

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• calculate read-only

  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".

  Parameters:

  • expression (required) — string — The expression to evaluate
  • decimals — integer — Optional: round the result to this many decimal places

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• convert_units read-only

  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.

  Parameters:

  • value (required) — number — The number to convert
  • from (required) — string — Unit to convert from, e.g. "mi", "pound", "°F", "GB"
  • to (required) — string — Unit to convert to, e.g. "km", "kg", "celsius", "GiB"

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• text_stats read-only

  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.

  Parameters:

  • text (required) — string — The text to analyze
  • count — string — Optional letter, word or substring to count occurrences of
  • overlapping — boolean — For `count`: count overlapping matches ("aa" in "aaa" = 2). Default false.
  • case_sensitive — boolean — For `count`. Default false.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• hash_text read-only

  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.

  Parameters:

  • text (required) — string
  • operation (required) — string

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• regex_test read-only

  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.

  Parameters:

  • pattern (required) — string — Regex pattern without slashes, e.g. "(\\d{3})-(\\d{4})"
  • text (required) — string
  • flags — string — Optional flags: i (ignore case), m (multiline), s (dotall), u (unicode), y (sticky). Global matching is always on.
  • max_matches — integer — Default 100
  • replace_with — string — Optional replacement string ($1, $<name> supported). If set, returns the replaced text too.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• validate_email read-only

  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.

  Parameters:

  • email (required) — string
  • check_dns — boolean — Also look up the domain's mail servers. Default false.

  Hints: read-only yes · destructive no · idempotent yes · open-world yes

• validate_phone read-only

  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.

  Parameters:

  • phone (required) — string
  • default_country — string — Two-letter country code used when the number has no "+" prefix, e.g. "US", "GB", "DE"

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• validate_url read-only

  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.

  Parameters:

  • url (required) — string
  • require_https — boolean — Treat http:// as invalid. Default false.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• validate_iban read-only

  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.

  Parameters:

  • iban (required) — string

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• json_repair read-only

  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.

  Parameters:

  • text (required) — string — The broken JSON text
  • pretty — boolean — Indent the output. Default false.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• json_schema_validate read-only

  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.

  Parameters:

  • data (required) — The JSON value to check (any type), or a JSON string of it
  • schema (required) — The JSON Schema (object), or a JSON string of it
  • draft — string — Default 2020-12

  Hints: read-only yes · destructive no · idempotent yes · open-world no

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