Locale-correctness tools for AI agents. Agents are systematically wrong about
everyday non-US data — they read 03/04 as March 4 in the UK, apply today's VAT
rate to a historical invoice, format €1,234.50 for a German reader, and miss
bank holidays in delivery dates. localecheck gives them verified answers and
flags impossible inputs instead of guessing.
Coverage: UK + USA (v1), expanding. Free, no API key.
Package | Install | Use | |
TypeScript (primary) |
| MCP server and importable library | |
Python | from source (PyPI release coming soon) | MCP server, importable library, REST API |
Both wrap the same authoritative libraries (libphonenumber, CLDR/Intl, date-holidays) and share the same hand-curated tax data.
Related MCP server: bizdays
parse_date · validate_phone · format_currency · tax_rate (VAT/sales-tax
by date) · is_holiday / next_holiday · parse_address
{ "mcpServers": { "localecheck": { "command": "npx", "args": ["-y", "localecheck"] } } }Then ask naturally — the agent picks the tool: "A UK invoice dated 1 June 2009 — what VAT rate?" → 15%.
packages/localecheck-ts — primary TypeScript package (MCP + library)
packages/localecheck-python — Python package + FastAPI REST API
eval/ — benchmark harness: how often raw LLMs get this wrong
benchmark.html — shareable results page · BUSINESS_MODEL.md — strategy ·
PUBLISH.md — release steps · LOCAL_TEST.md — test before publishing
UK VAT history is reliable for the modern era (standard rate). US state sales-tax values are 2025 state base rates (local taxes add on top) — verify against an authoritative feed before live invoicing. Addresses parse + extract a valid postcode/ZIP but don't verify deliverability.
Code: Apache-2.0. Curated tax data: see BUSINESS_MODEL.md.
Format a money amount the way a reader in a given locale expects (symbol position, decimal/thousands separators). USE THIS whenever you show a price/total to a user or put one in an email, invoice, or report. e.g. 1234.5 GBP en-GB -> '£1,234.50'.
Inputs: amount (required), currency, locale.
Check whether a date (YYYY-MM-DD) is a public/bank holiday. USE THIS when computing business-day deadlines, delivery SLAs, or 'next working day'. GB defaults to England; pass subdiv 'SCT'/'WLS'/'NIR' or a US state code. Country is GB or US.
Inputs: date (required), country, subdiv.
Find the next public/bank holiday on or after a date (default today). USE THIS to answer 'when is the next holiday' or find the next working day. Country is GB or US; subdiv narrows to a UK nation or US state.
Inputs: country, after, subdiv.
Extract structured {country, postcode, city} from a free-text UK or US address. USE THIS when onboarding a user, running a KYC/fraud check, or storing an address, instead of splitting the string yourself. Returns a confidence flag.
Inputs: input (required).
Convert a human-written date into ISO 8601 (YYYY-MM-DD). USE THIS whenever you need to interpret a date a person typed — especially ambiguous numeric dates like 03/04/2025, which mean different things in the UK (day-first) vs US (month-first) — before storing, scheduling, or acting on it. Pass locale 'en-GB' or 'en-US'. Returns valid:false for impossible dates.
Inputs: input (required), locale.
Look up the correct consumption-tax rate. USE THIS before calculating VAT or sales tax on an invoice or quote — never recall the rate from memory, it is DATE-SENSITIVE. GB returns the UK standard VAT rate that applied on the given date (handles historical/temporary changes). US has no national VAT (returns 0); pass a state code like 'CA' for the state base sales-tax rate. Always pass the invoice date for GB.
Inputs: country, date, state.
Validate a phone number and normalise it to E.164 (e.g. +442079460958). USE THIS before saving a phone number, dialling, or sending an SMS, instead of trusting raw input. Pass region 'GB' or 'US'. Returns valid:false if the number is not real for that region.
Inputs: number (required), region.
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Scored across 7 tools
Each tool targets a distinct locale-related function (currency, holiday, address, date, tax, phone) with no overlap.
All tool names follow a consistent verb_noun pattern in snake_case, making the set predictable.
Seven tools is well-scoped for a locale utility server, covering formatting, validation, and lookups without being excessive or too few.
Covers key locale operations (currency, dates, addresses, phones, holidays, taxes) but lacks timezone or unit conversion, which are minor gaps.
Address validation & geocoding for AI agents: 240+ countries, UK PAF, free US/CA enrichment
Utility data for AI agents: IBAN, EU holidays, VAT rates, time zones, ECB FX. Pay per call.
Validate EU, UK, AU VAT numbers for AI agents. EU ViDA e-invoicing compliance.
15 deterministic validation tools for AI agents: tax IDs (15 countries), VAT, IBAN, LEI, HS codes.
