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FabTally Utility Belt

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13 deterministic agent utilities: timezone, cron, RRULE, currency, regex, diff, hashing & more.

Source code Website Documentation

Install

Add this to your client's MCP configuration (Claude Desktop: claude_desktop_config.json; Cursor: .cursor/mcp.json; VS Code and others use the same "mcpServers" shape).

Remote (streamable-http)
Claude Code 
claude mcp add --transport http fabtally-utility-belt 'https://belt.fabtally.com/mcp'
JSON configuration (Claude Desktop, Cursor, VS Code) 
{
    "mcpServers": {
        "fabtally-utility-belt": {
            "type": "http",
            "url": "https://belt.fabtally.com/mcp"
        }
    }
}

Documentation

From the project's README on GitHub, refreshed weekly. Links open on GitHub.

Contents
  1. FabTally Utility Belt — MCP server
  2. Tools
  3. Install / run
  4. Paying for paid tools
  5. Guarantees

FabTally Utility Belt — MCP server

The deterministic micro-utilities AI agents call constantly, as an MCP server (stdio + streamable-HTTP) and a pay-per-call HTTP API. One reliable bundle instead of thirteen flaky npm deps.

  • Free tools return real results with no wallet: convert, text, hash, encode, id, regex.
  • Paid tools ($0.001/call, x402 · USDC on Base): timezone, cron, rrule, currency, diff, jsonschema, datemath. With no payment a paid tool returns the decoded x402 402 challenge (price / network / asset / payTo) so an agent can pay and retry with x_payment. Humans can instead prepay by card and use an X-FabTally-Key credit key against the HTTP API.

This server holds no private key. It fronts https://belt.fabtally.com. Every utility is a pure, deterministic function with strict input validation; bad input → 400, never charged; nothing is stored.

Tools

ToolTierWhat it does
convertfreeUnit conversion (length/mass/temperature/volume/data/time/area/speed/angle/pressure/energy).
textfreeslugify · case-convert (camel/pascal/snake/kebab/constant/…) · {{template}} fill.
hashfreesha256/sha512/sha384/sha1/md5/sha3-256/keccak256/ripemd160, optional HMAC, hex/base64 out.
encodefreebase64 / base64url / hex / url / html encode & decode.
idfreeuuid v4/v7, ULID, nanoid, random hex/base64url/int (count up to 1000).
regexfreetest/match/extract/replace with catastrophic-backtracking protection (killable worker + timeout).
timezone$0.001Instant → IANA zone with historically-correct DST; offsets, abbreviations, DST flags.
cron$0.001Cron expression → next N run times + plain-English description.
rrule$0.001iCal RRULE (RFC 5545) → next N occurrences.
currency$0.001Live currency conversion at reference/mid-market rates (keyless ECB feed, cached).
diff$0.001Text diff: unified patch + structured op-list + add/remove/hunk stats.
jsonschema$0.001Validate against JSON Schema (draft 2020-12) and explain every error in plain English.
datemath$0.001Add/subtract ISO-8601 durations, diff into chosen units, business-day add/diff.

Install / run

stdio (Claude Desktop, Cursor, any MCP client)
// claude_desktop_config.json
{
  "mcpServers": {
    "fabtally-belt": { "command": "npx", "args": ["-y", "fabtally-belt-mcp"] }
  }
}

Or clone and run: node index.js (speaks MCP over stdio).

streamable-HTTP (remote)

Hosted: https://belt.fabtally.com/mcp. Or self-host: MCP_HTTP_PORT=8108 node http.js.

Config
  • FABTALLY_BELT_BASE — API base (default https://belt.fabtally.com).

Paying for paid tools

A paid tool with no x_payment returns:

{ "payment_required": true, "http_status": 402,
  "challenge": { "x402Version": 2, "accepts": [ { "scheme": "exact", "network": "eip155:8453",
    "amount": "1000", "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913", "payTo": "0x…" } ] } }

Build an x402 payment authorization (EIP-3009 transferWithAuthorization to payTo) for the accepts entry and call the tool again with the token in x_payment. amount is atomic USDC (1000 = $0.001).

Guarantees

Deterministic. Stateless — no PII or request data stored. Receive-only wallet (no custody). Currency figures are reference/mid-market rates for informational use, not a dealable quote. MIT licensed.

Frequently asked questions

What is FabTally Utility Belt?

13 deterministic agent utilities: timezone, cron, RRULE, currency, regex, diff, hashing & more.

How do I install FabTally Utility Belt?

It runs as a remote server. In Claude Code: claude mcp add --transport http fabtally-utility-belt 'https://belt.fabtally.com/mcp'. For other clients, paste the JSON configuration from this page into their MCP settings.

Does FabTally Utility Belt need an API key?

Its registry entry lists no required key or secret. Some features may still need an account with the service it connects to.

Is FabTally Utility Belt open source?

Yes. Its code is on GitHub under the MIT license.

Who maintains FabTally Utility Belt?

It is published by zvmzaretsky. AI.tn lists it but does not maintain or endorse it.

From the official MCP Registry. Listing is not an endorsement: review a server's code and permissions before giving it access to your data.