Calc Mcp

io.github.coo-quackPublished by GitHub account coo-quackv2.1.5Updated Oct 25, 2026

21 MCP tools for math, randomness, dates, encoding, hashing, and more — deterministic and accurate.

The publisher's own server: calc.engineer

VerifiedSTDIODesktop onlyDeveloper Tools Data & Analytics

Server details

Identifier: io.github.coo-quack/calc-mcp
Transport: STDIO
Runtime: Desktop only
Trust: Verified
Published: Sep 16, 2026

Security note

MCP servers receive tool arguments from a conversation and may perform external actions. Review what a server can do before you enable it, and give it only the access it needs.

The registry verified the GitHub account coo-quack for this listing. That does not show the account is the product's maker.

SourceWeft's checks cover whether the listing is complete and the endpoint answered; they do not review the server's code or what its tools do.

Add a badge to your README

Show readers this MCP server is listed on SourceWeft. The badge links to this page.

[![Listed on SourceWeft](https://sourceweft.com/badge/mcp/io.github.coo-quack%2Fcalc-mcp.svg)](https://sourceweft.com/mcp/io.github.coo-quack%2Fcalc-mcp?utm_source=readme&utm_medium=badge)

Overview

AI-generated overview

A local stdio MCP server with 21 deterministic utility tools for math, randomness, dates, encoding, hashing, parsing and unit conversion.

What you can do: Evaluate math expressions and statistics, convert number bases, and validate or generate Luhn check digits
Generate UUIDs, ULIDs, passwords, random numbers and shuffled lists, and compute hashes or HMACs
Encode and decode Base64, URL, HTML and Unicode, and count characters, words, lines and bytes
Work with dates and times: current time, timezone conversion, date arithmetic, UNIX timestamps and cron schedules
Parse and analyze text: regex test/match/replace, line diffs, Levenshtein distance, JSON/CSV/XML/YAML validation, Unicode character info
Convert units and colors, inspect IP addresses and CIDR ranges, parse URLs, compare semantic versions, and decode JWT headers and payloads
When to use it: Useful when an assistant needs exact arithmetic, real randomness, reliable timezone and date math, or repeatable encoding, hashing and parsing results instead of guessing. A good fit for everyday developer and data chores that should be deterministic and stay on the local machine.
Requirements: Runs as a local process over stdio, started with npx from the npm package (Node.js required) or from the published Docker image. No account, API key or environment variables are needed.

Before you install

The hash tool warns that MD5 and SHA-1 are cryptographically broken and should not be used for security. The JWT tool only decodes and does not verify signatures, so its output must not be trusted for authentication. Computation is local, but anything passed to the tools is sent to whichever LLM provider you use, so avoid real secrets and production credentials.

Installation

In SourceWeft

Open Calc Mcp in the dashboard and add it to a workspace.
Enable the server for the chats that should use its tools.

Desktop only via STDIO. STDIO servers start a local process, so they need the SourceWeft desktop host.

Other MCP clients

Follow the launch instructions in the repository.

README

Calc MCP

[npm version] [CI] [License: MIT]

[Calc MCP demo]

📖 Documentation — Full tool reference, examples, and install guides.

21 tools for things AI is not good at — deterministic math, cryptographic randomness, accurate date arithmetic, encoding, hashing, and more.

LLMs hallucinate calculations, can't generate true random numbers, and struggle with timezones. This MCP server fixes that.

Quick Start

bash

# Claude Codeclaude mcp add -s user calc-mcp -- npx -y @coo-quack/[email protected]
# Or just run itnpx -y @coo-quack/[email protected]

# Claude Codeclaude mcp add -s user calc-mcp -- npx -y @coo-quack/[email protected]
# Or just run itnpx -y @coo-quack/[email protected]

Works with Claude Desktop, VS Code Copilot, Cursor, Windsurf, and any MCP client — setup guides below.

Why?

AI alone	With calc-mcp
"10 + 34 × 341 ÷ 23 = 507.8" ❌	`514.087` ✅ (math)
"Here's a UUID: 550e8400-..." 🤷 fake	Cryptographically random UUID v4/v7 ✅ (random)
"100 days from now is..." 🤔 guess	`2026-05-22` ✅ (date)
"SHA-256 of password123 is..." 💀 hallucinated	`{"hash": "ef92b778bafe..."}` ✅ (hash)

Deterministic — Same input, same correct output, every time
Secure — Sandboxed math, ReDoS protection, weak hash warnings
Private — All computation runs locally, no data sent to external services
No server config — Install once via npx; MCP client setup required
No API key — No account or API key required for calc-mcp itself; requires Node.js

Examples

Ask in natural language — your AI assistant selects the appropriate tool.

Math & Numbers

Text & Encoding

You ask	You get	Tool
How many characters in "Hello, World! 🌍"?	`15 chars, 18 bytes`	count
Base64 encode "Hello World"	`SGVsbG8gV29ybGQ=`	base64
Base64 decode "eyJhbGciOiJIUzI1NiJ9"	`{"alg":"HS256"}`	base64
URL-encode "hello world"	`hello%20world`	encode
URL-decode "hello%20world"	`hello world`	encode
HTML-decode `<script>`	`<script>`	encode
SHA-256 hash of "password123"	`{"hash": "ef92b778bafe..."}`	hash
HMAC-SHA256 of "message" with key "secret"	`{"hash": "8b5f48702995..."}`	hash

Date & Time

Generation

Conversion

Analysis & Parsing

You ask	You get	Tool
Extract numbers from "abc123def456"	`123, 456`	regex
Does 1.5.3 satisfy ^1.0.0?	`true`	semver
Does 1.8.0 satisfy ">=1.5.0 <2.0.0"?	`true`	semver
IP range of 192.168.1.0/24?	`192.168.1.1 – .254 (254 hosts)`	ip
Edit distance: "kitten" → "sitting"	`3`	diff
Unicode info for "€"	`U+20AC, Currency Symbols`	char_info
Is `{"name":"test"}` valid JSON?	`valid, object`	format_validate

Decode & Parse

All 21 Tools

Tool	Description
`math`	Evaluate expressions, statistics
`count`	Characters (grapheme-aware), words, lines, bytes
`datetime`	Current time, timezone conversion, UNIX timestamps
`random`	UUID v4/v7, ULID, passwords (readable, custom charset), random number, shuffle
`hash`	MD5, SHA-1, SHA-256, SHA-512, CRC32, HMAC
`base64`	Encode / decode
`encode`	URL, HTML entity, Unicode escape
`date`	Diff, add/subtract, weekday, wareki
`regex`	Test, match, matchAll, replace
`base`	Number base conversion (2–36)
`diff`	Line diff, Levenshtein distance
`format_validate`	Validate JSON, CSV, XML, YAML
`cron_parse`	Human-readable cron + next runs (weekday/month names supported)
`luhn`	Validate / generate check digits
`ip`	IPv4/IPv6 info, CIDR contains check, range calculation
`color`	HEX ↔ RGB ↔ HSL (alpha channel supported)
`convert`	8 categories, 146 unit names: length, weight, temperature, area (tsubo, tatami), volume, speed, data, time
`char_info`	Unicode code point, block, category
`jwt_decode`	Decode header + payload (no verification)
`url_parse`	Protocol, host, path, params, hash
`semver`	Compare, validate, parse, range satisfaction

Install

Claude Code

Claude Code plugin

Also available as a plugin from the coo-quack marketplace:

See the installation guide for details.

Claude Desktop / Cursor / Windsurf

Add to your config file:

App	Config path
Claude Desktop (macOS)	`~/Library/Application Support/Claude/claude_desktop_config.json`
Claude Desktop (Windows)	`%APPDATA%\Claude\claude_desktop_config.json`
Cursor	`~/.cursor/mcp.json`
Windsurf	`~/.codeium/windsurf/mcp_config.json`

json

{  "mcpServers": {    "calc-mcp": {      "command": "npx",      "args": ["-y", "@coo-quack/[email protected]"]    }  }}

{  "mcpServers": {    "calc-mcp": {      "command": "npx",      "args": ["-y", "@coo-quack/[email protected]"]    }  }}

VS Code (GitHub Copilot)

Add to .vscode/mcp.json in your workspace:

json

{  "servers": {    "calc-mcp": {      "command": "npx",      "args": ["-y", "@coo-quack/[email protected]"]    }  }}

{  "servers": {    "calc-mcp": {      "command": "npx",      "args": ["-y", "@coo-quack/[email protected]"]    }  }}

Docker Image

Calc MCP is available as a Docker image from GitHub Container Registry:

Or use in MCP client config:

json

{  "mcpServers": {    "calc-mcp": {      "command": "docker",      "args": ["run", "--rm", "-i", "ghcr.io/coo-quack/calc-mcp:latest"]    }  }}

{  "mcpServers": {    "calc-mcp": {      "command": "docker",      "args": ["run", "--rm", "-i", "ghcr.io/coo-quack/calc-mcp:latest"]    }  }}

Available tags:

ghcr.io/coo-quack/calc-mcp:latest — Latest release
ghcr.io/coo-quack/calc-mcp:X.Y.Z — Specific version (replace X.Y.Z with the desired version)

Other MCP Clients

Calc MCP works with any MCP-compatible client. Run the server via stdio:

Point your client's MCP config to the command above. The server communicates over stdio using the standard Model Context Protocol.

Development

bash

bun installbun run dev       # Start dev serverbun test          # Run testsbun run lint      # Biomebun run format    # Biome

bun installbun run dev       # Start dev serverbun test          # Run testsbun run lint      # Biomebun run format    # Biome

Security

calc-mcp processes all data locally and does not:

❌ Send data to external servers
❌ Log data to files or remote services
❌ Store processed data persistently

For detailed security information, see SECURITY.md.

Safe Usage with LLMs

calc-mcp itself is local-only. However, when used via an LLM, your inputs are sent to the LLM provider (Anthropic, OpenAI, etc.).

✅ DO: Use test/sample data when possible
✅ DO: Use local-only LLMs for sensitive operations
❌ DON'T: Pass production secrets to MCP tools (they will be sent to your LLM provider)

Example:

bash

# ❌ Unsafe: Any secret passed to MCP tool is sent to your LLM provider# Tool: hash# Input: { "input": "sk-1234567890abcdef", "algorithm": "sha256" }
# ✅ Safe: Use test data only (for learning/development)# Tool: hash# Input: { "input": "test-value-123", "algorithm": "sha256" }
# ✅ For production secrets: Use local-only LLMs or process outside MCP

# ❌ Unsafe: Any secret passed to MCP tool is sent to your LLM provider# Tool: hash# Input: { "input": "sk-1234567890abcdef", "algorithm": "sha256" }
# ✅ Safe: Use test data only (for learning/development)# Tool: hash# Input: { "input": "test-value-123", "algorithm": "sha256" }
# ✅ For production secrets: Use local-only LLMs or process outside MCP

Note: Error messages are automatically sanitized to prevent accidental data leakage.

For security issues, please see our Security Policy.

License

MIT

Source: README.md at commit 5b71335

Tools

random

Generate random values: UUID, ULID, secure password (with fine-grained options), random number, or shuffle a list

ParametersmaxmintyperequireditemslengthcharsetnumberssymbolsreadableuppercaseuuidVersionexcludeChars

hash

Compute hash or HMAC of a string using MD5, SHA1, SHA256, SHA512, or CRC32. WARNING: MD5 and SHA1 are cryptographically broken and MUST NOT be used for security (use SHA-256 or SHA-512 instead).

Parameterskeyinputrequiredactionalgorithmrequired

base64

Encode or decode Base64 strings

Parametersinputrequiredactionrequired

encode

Encode or decode strings using URL, HTML, or Unicode encoding

Parameterstyperequiredinputrequiredactionrequired

datetime

Get current datetime, convert timezones, format dates, and convert UNIX timestamps

ParametersactionrequiredformatdatetimetimezonetimestamptoTimezonefromTimezone

count

Count characters (grapheme clusters), words, lines, and bytes in text

Parameterstextrequiredencoding

math

Evaluate math expressions or compute statistics on numbers

Parametersactionvaluesexpression

date

Date calculations: diff between dates, add to date, weekday, and Japanese wareki conversion

Parametersdaterequiredunitdate2actionrequiredamount

regex

Test, match, matchAll, or replace using regular expressions

Parameterstextrequiredflagsactionrequiredpatternrequiredreplacement

base

Convert numbers between bases (2-36), supports large numbers via BigInt

Parameterstorequiredfromrequiredvaluerequired

diff

Compare two texts: line-by-line diff (Myers algorithm, falls back to full replacement if edit distance exceeds 1000) or Levenshtein distance

Parameterstext1requiredtext2requiredaction

format_validate

Validate and parse JSON, CSV, XML, or YAML strings

Parametersinputrequiredformatrequired

cron_parse

Parse cron expression and return next N execution times

Parameterscounttimezoneexpressionrequired

luhn

Validate or generate check digits using the Luhn algorithm

Parametersactionnumberrequired

ip

IP address info, CIDR contains check, and range calculation

Parametersipcidractionrequiredtarget

color

Convert colors between HEX, RGB, and HSL formats

Parameterstocolorrequired

convert

Convert between units: length, weight, temperature, area, volume, speed, data, time

Parameterstorequiredfromrequiredvaluerequiredcategory

char_info

Get Unicode information about characters (code point, block, category)

Parameterscharrequired

jwt_decode

Decode JWT token header and payload for inspection only. WARNING: this tool does NOT verify the signature; never trust the payload for authentication or authorization without separate signature verification using the issuer's verification key (shared secret or public key, depending on alg).

Parameterstokenrequired

url_parse

Parse a URL into its components (protocol, host, path, params, etc.)

Parametersurlrequired

semver

Semantic versioning: compare, validate, and check range satisfaction

Parametersrangeactionrequiredversionrequiredversion2

Version history

v2.1.5LatestOct 25, 2026
v2.1.4Oct 13, 2026
v2.1.3Oct 11, 2026
v2.1.2Sep 26, 2026
v2.1.1Sep 16, 2026

Score

90% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

Reached in the last 30 days25 pts
Auth declared10 pts
Declare the credential headers in the registry entry, or keep the endpoint answering the probe so its auth can be classified.
Tools listedRequired15 pts
DescriptionRequired15 pts
Logo10 pts
Documentation15 pts
License10 pts

Other Calc integrations

calc.engineer

engineer.calcOfficial publisher

Keyless remote MCP server offering 88 engineering calculators for RF links, LoRa/Meshtastic, PCB, thermal, power and homelab planning.

Streamable HTTPWeb executable

Cloud & Infrastructure89 toolsOct 24, 2026

DeskCalc Verify

com.deskcalc

A local stdio MCP server that lets an assistant hand invoice, receipt and statement figures to a human for checking and confirmation in DeskCalc.

STDIODesktop only

FinanceNot validated yetNov 7, 2026

Finance Calc Mcp

Published by GitHub account mrfentmen

A local stdio MCP server for finance math: loan payments, amortisation schedules, compound interest and net present value, computed offline.

STDIODesktop only

FinanceNot validated · the server did not startOct 30, 2026

Stem Calc Student Mcp

Published by GitHub account AnonymousOnyx22

A local, offline calculator server that lets an assistant compute molar masses, balance equations, do stoichiometry and convert units reliably.

STDIODesktop only

5 toolsNov 8, 2026

PJe-Calc MCP

Published by GitHub account lucianumm

Local MCP server that lets a desktop AI assistant build, audit, update and check Brazilian labor-court calculations inside PJe-Calc Cidadão on Windows.

STDIODesktop only

Productivity & WorkflowNot validated · the package type cannot run in the sandboxOct 25, 2026

You ask	You get	Tool
100 miles in kilometers?	`160.93 km`	convert
72°F in Celsius?	`22.22°C`	convert
Convert #FF5733 to RGB	`rgb(255, 87, 51)`	color
Convert rgba(255, 0, 0, 0.5) to 8-digit HEX	`#ff000080`	color

You ask	You get	Tool
What time is it in New York?	`2026-02-10T19:00:00-05:00`	datetime
What's 100 days after 2026-02-11?	`2026-05-22`	date
When does "30 9 * * 1-5" run?	`Mon–Fri at 9:30`	cron_parse

You ask	You get	Tool
Decode this JWT: eyJhbGci...	`{ alg: "HS256", name: "John Doe" }`	jwt_decode
Parse https://example.com/search?q=hello	`host: example.com, q: "hello"`	url_parse