Use this when the user asks 'what is X in Y?', 'convert X to Y', 'current rate of EUR/USD', or any single fiat-to-fiat live exchange rate question. Returns the latest mid-market rate as a JSON object like { rate: 0.9234, source } meaning 1 source = 0.9234 target. Without an API key it answers from an official central-bank table instead (ECB first, else the bank that issues one of the two currencies) and says so in note — relay the rate_date; pairs no single bank publishes (or inverts) need a key. Does NOT support cryptocurrencies, commodities, or arithmetic on amounts. For multiple targets in one call use get_rates_authenticated; for a past date or fixed lookback (7d/30d/1y) use get_historical_rates.

Use this for fixed-window time-series questions like 'how has EUR/USD moved this week', 'show me the last month of GBP/JPY', or 'chart 1-year history of AUD/USD'. Returns { source, target, period, data: [{ date, rate, timestamp }, ...] } — sampling is fixed per period (1d=hourly, 7d/30d=daily, 1y=weekly) and the window always ends NOW. Needs an API key on a paid plan; free and trial keys get a 403. For a specific past datetime use get_rates_authenticated with time. For a single live rate use get_exchange_rate.

Use this for (a) one source against multiple targets in a single call ('USD vs EUR, GBP, JPY'), or (b) the rate at a specific past datetime ('EUR/USD at 2025-03-14T12:00Z'), optionally bucketed by hour/day/week/month. Returns { rates: [{ rate, source, target, time }, ...] } — one row per target × time bucket. Multi-target latest rates work on any key; a past datetime (time) needs a paid plan. For a single live pair use get_exchange_rate. For fixed lookback windows (1d/7d/30d/1y ending now) use get_historical_rates.

Call this BEFORE other tools when you are unsure whether a currency code is supported, or when the user asks 'what currencies do you support?', 'is X a valid currency?', or 'what is the symbol for X?'. Returns { currencies: [{ code: 'USD', name: 'US Dollar', symbol: '$' }, ...], count } covering 160+ ISO 4217 fiat currencies. Does NOT include cryptocurrencies. Cheap to call (cached 24h upstream) — use it to validate user input and prevent downstream errors in get_exchange_rate / get_rates_authenticated / get_historical_rates.

Call this FIRST when you need a bank code, or for 'which central banks do you cover?' / 'do you have rates from X?'. Returns every covered source — 121 central banks plus 3 tax authorities (HMRC, US Treasury, Swiss BAZG) — with code (what get_official_rates takes as bank), name, latest publication date and whether it is behind schedule. No API key needed.

OFFICIAL rates a named institution published — 'what is the ECB rate for USD?', 'Bank of Japan rate today', 'HMRC rate for invoicing'. These are the fixed, citable rates for compliance, tax, customs and accounting — NOT live market rates (use get_exchange_rate for those). Omit date for the newest published table (no API key needed); give date (API key, paid plan) for the table in force that day — weekends/holidays roll back to the last published date and the response's rate_date says which. Omit source/target for the full table; give both for one pair — cross-computed inside the bank's own table when not directly published, flagged derived. Always cite the returned rate_date.

AllRatesToday's once-a-day, never-revised mid-market rate: the per-currency median of samples in a five-minute window centred on 16:00 London, published each business day. Use it when the user needs ONE reproducible rate per day — index levels, return series, research datasets, month-end reports — rather than a live quote (get_exchange_rate) or an institution's official rate (get_official_rates). Omit source/target for the whole table; give both for one pair (crossed via USD, flagged derived). Omit date for the latest table (no key needed); give date (API key, paid plan) for a past business day. Not the WM/Refinitiv fix and not a registered benchmark — relay the disclaimer and the rate_date.

Self-issue an AllRatesToday API key with 100 lifetime calls, valid 7 days, with no account and no email. Use it when another tool answered "needs an API key" and the user wants real-time rates or history right now. The key is adopted by this server for the rest of the session and returned once — tell the user to put it in the MCP config as ALLRATES_API_KEY to keep it. Capped at 3 keys per IP per day. For a lasting key, register at https://allratestoday.com/register (free, 300 calls) or see https://allratestoday.com/pricing.