Show HN: A free MCP server for facts LLMs get wrong (time zones, holidays, FX)

APIStack released a free Model Context Protocol server that gives AI agents such as Claude, ChatGPT and Cursor 16 deterministic tools for facts the company says LLMs get wrong, including current time, public holidays, working days, currency conversion, EU VAT and IBAN validation, company lookups, URL safety checks and sanctions screening. The server at apistack.online/api/mcp/facts requires no sign-up and allows 50 free calls a day, with a free API key needed beyond that limit; a separate unified endpoint exposes three tools (search_apis, get_api_details, call_api) to keep context use low. Single-purpose servers with hand-written tools require a Pro or Enterprise subscription, while the unified endpoint works on every plan.

Give AI agents like Claude, ChatGPT and Cursor exact, deterministic tools through the Model Context Protocol No sign-up needed · 50 free calls a day 16 focused tools for questions agents should not answer from memory: the current time, holidays and working days, exchange rates, VAT and IBAN checks, company lookups, link safety, sanctions screening and more. Add the URL and it works right away; add a free API key when you need more than 50 calls a day. https://apistack.online/api/mcp/facts claude mcp add --transport http apistack-facts https://apistack.online/api/mcp/facts get current time · Current time in a time zone find meeting time · Shared working hours across time zones list public holidays · Public holidays check working day · Is a date a working day? add working days · Add working days date difference · Difference between two dates convert currency · Convert currency validate vat number · Check an EU VAT number validate iban · Validate an IBAN validate email · Validate an email address validate phone · Validate a phone number lookup company · Look up a company check url safety · Check if a link looks risky geocode city · Find a city screen sanctions · Screen a name against sanctions lists economic snapshot · Economic indicators for a country Full catalog · API key Add one MCP server and your agent can search the whole catalog, read an API's details and run it: three tools search apis , get api details , call api instead of dozens, so it stays light on context. ?categories=finance,utilities or ?apis=email-address-validator to the URL https://apistack.online/api/mcp/connect Replace YOUR API KEY with the key from your dashboard https://apistack.online/dashboard free account works . claude mcp add --transport http apistack https://apistack.online/api/mcp/connect \ --header "x-api-key: YOUR API KEY" Watch the 90-second setup · 1:34 Connect APIStack to Claude Code, Cursor, VS Code or your own agent, with a real agent run. Single-purpose servers with hand-written tools Pro and Enterprise . Dedicated servers require a PRO or Enterprise subscription the unified endpoint above works on every plan . Sign in https://apistack.online/sign-in to access. AI-ready Model Context Protocol MCP servers that integrate with your AI tools. Bridge your applications and AI assistants with contextual, data-aware conversations. Our MCP servers are currently in development. We're working hard to bring you powerful, context-aware integrations that will revolutionize how you interact with AI. Stay tuned for updates on our progress