calc_subnet
Calculate subnet details (network, broadcast, usable hosts, mask) from a CIDR like 192.168.1.0/24
cidrrequired
io.github.headlessherm-creatorPublished by GitHub account headlessherm-creatorv3.1.0Updated Oct 29, 2026
Local deterministic calc MCP: exact math, dates, unit conversion, stats, subnet math.
Local MCP server giving assistants exact, deterministic math, date, unit, statistics, subnet and UUID tools with no network calls.
Desktop only via STDIO. STDIO servers start a local process, so they need the SourceWeft desktop host.
Follow the launch instructions in the repository.
A free, local, 16-tool MCP server that gives AI agents exact, deterministic answers for math, date arithmetic, unit conversion, subnet/networking calculations, statistics, token counting, and real random UUID generation — no network calls, no API keys, no telemetry.
If your AI agent is miscounting days between dates, rounding large numbers incorrectly, getting unit conversions slightly wrong, or messing up subnet/CIDR math, this MCP server exists specifically to fix that class of problem.
Local and open-weight models (Llama, Qwen, Mistral, etc.) are consistently unreliable at exact math, date arithmetic, unit conversion, and similar deterministic tasks — they "reason" their way to an answer instead of computing it, and get it subtly wrong. (Frontier hosted models like Claude and GPT-4 already handle most of this correctly unaided — this toolkit is aimed at closing the gap for smaller/local models, not replacing what those already do well.) Every tool here uses classical deterministic methods instead of model reasoning, so the answer is always exactly right.
Everyday things it fixes:
More technical tools:
Most AI dev tool MCP servers either charge a subscription or call out to a remote API. This one never touches the network. Every tool is pure local computation, verifiable directly in the source: open src/tools.js — there is no fetch or http import anywhere in it.
1. Install Node.js (v18+) if you don't have it: https://nodejs.org
2. Clone this repo and install dependencies:
3. Point your MCP client at the local path:
Add that to your MCP client's config and restart it. Setup docs for common clients:
calculate (arbitrary-precision expression evaluator),
factorial, permutations, combinations (all arbitrary-precision, avoid float64
overflow), compute_statistics (mean, median, stdev, variance, percentiles)date_add, date_diff (leap years, month boundaries, business
days handled correctly), convert_timezoneconvert_unit (length, weight, volume, temperature), convert_base
(decimal, hex, binary, octal)calc_subnet (CIDR math), check_ip_type (private/reserved range
lookup)levenshtein_distance (exact edit distance and similarity ratio)haversine_distance (exact great-circle distance between coordinates)count_tokens (GPT tokenizer, for managing context budget before
a large prompt), generate_uuid (real cryptographically-random v4 UUIDs, 1-100 at a time)@modelcontextprotocol/sdk: the MCP protocol implementationzod: input schema validationmathjs: arbitrary-precision math evaluationgpt-tokenizer: GPT tokenizer for count_tokensAll installed automatically by npm install. None of them make network calls at runtime.
deterministic math MCP server, MCP date calculator, MCP unit converter, subnet CIDR calculator MCP, local MCP server no API key, Claude MCP math tools, AI agent exact arithmetic, token counter MCP server.
Same local-first philosophy, different problems:
MIT
Source: README.md at commit 4e2f25a
Calculate subnet details (network, broadcast, usable hosts, mask) from a CIDR like 192.168.1.0/24
cidrrequiredCheck if an IPv4 address is private/reserved and identify which range it falls in
iprequiredEvaluate an arbitrary-precision math expression exactly (fixes LLM multi-digit arithmetic errors). Supports +,-,*,/,^,sqrt(),sin(),log(), etc.
expressionrequiredCount tokens in text using the GPT-3.5/4 (cl100k_base) tokenizer. Useful for managing context budget before sending a large prompt
textrequiredAdd or subtract days/weeks/months/years/businessDays from a date, handling leap years and month boundaries correctly
daterequiredunitrequiredamountrequiredCompute the exact difference between two dates in days, business days, and hours
arequiredbrequiredConvert a UTC/ISO date into a formatted date+time string for any IANA time zone
daterequiredtimeZonerequiredCompute mean, median, stdev, variance, min/max, and percentiles (25/75/90) for a list of numbers
numbersrequiredConvert a value between units of length, weight, volume, or temperature (fixes LLM unit-math errors)
valuerequiredtoUnitrequiredfromUnitrequiredCompute exact great-circle distance in km/miles between two lat/long coordinates
lat1requiredlat2requiredlon1requiredlon2requiredCompute n! exactly using arbitrary-precision integer math (avoids float64 overflow past ~18)
nrequiredCompute nPr (permutations) exactly using arbitrary-precision integer math
nrequiredrrequiredCompute nCr (combinations) exactly using arbitrary-precision integer math
nrequiredrrequiredConvert a number between decimal, hex, binary, and octal
valuerequiredtoBaserequiredfromBaserequiredCompute exact edit distance and similarity ratio between two strings (deterministic fuzzy matching)
arequiredbrequiredGenerate real cryptographically-random UUIDs (v4). Fixes LLMs fabricating plausible-looking but non-random, potentially colliding UUID strings instead of real random ones.
count90% 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.
Declare the credential headers in the registry entry, or keep the endpoint answering the probe so its auth can be classified.
git clone https://github.com/headlessherm-creator/polymath-megablaster-mcp.gitcd polymath-megablaster-mcpnpm install{ "mcpServers": { "polymath": { "command": "node", "args": ["/absolute/path/to/polymath-megablaster-mcp/src/index.js"] } }}