# foster-mcp: CBRT (TCMB) exchange rates

> Official daily indicative exchange rates of the Central Bank of the Republic of Türkiye (CBRT/TCMB), served as a JSON REST API and a remote MCP server. Free, no API key. Rates are quoted in Turkish lira (TRY) per unit of foreign currency.

## Key facts

- Source: TCMB daily bulletin (https://www.tcmb.gov.tr/kurlar/). Every response includes `source_url`, `bulletin_date` and a disclaimer.
- Publication: business days around 15:30 Türkiye time (UTC+3). Dates always mean the bulletin's publication date.
- Weekends and holidays have no bulletin: the previous bulletin is returned with `is_fallback: true` and a `fallback_reason`.
- Rate types: `forex_buying`, `forex_selling` (default), `banknote_buying`, `banknote_selling`. Some currencies have no banknote rates (null).
- `unit`: rates are per this many units (JPY is per 100). Conversions divide by it.
- Decimals are strings; never parse them as floats for money.
- History back to 1996. Bulletins before 2005-01-01 are in old lira (`domestic_currency: "TRL"`; 1 TRY = 1,000,000 TRL).
- Rates are indicative; for official or legal use, check tcmb.gov.tr.

## REST endpoints

- [Latest rates](https://foster-mcp.esakiz.workers.dev/v1/rates/latest?currencies=USD,EUR): latest published bulletin
- [Rates on a date](https://foster-mcp.esakiz.workers.dev/v1/rates/2026-10-27): bulletin for YYYY-MM-DD, or the previous one (flagged)
- [Convert](https://foster-mcp.esakiz.workers.dev/v1/convert?from=USD&to=EUR&amount=100): TRY allowed on either side; optional `date` and `rate_type`. Cross conversions use the same rate type on both legs via TRY.
- [Currencies](https://foster-mcp.esakiz.workers.dev/v1/currencies): supported codes, names, units and available rate types
- [Health](https://foster-mcp.esakiz.workers.dev/health): data freshness
- [OpenAPI 3.1](https://foster-mcp.esakiz.workers.dev/openapi.json)
- [Error codes](https://foster-mcp.esakiz.workers.dev/errors): errors are RFC 9457 `application/problem+json`

## MCP

Remote MCP server (Streamable HTTP): https://foster-mcp.esakiz.workers.dev/mcp
Tools: get_latest_rates, get_rates_on_date, convert_currency, list_currencies.

# Türkiye business calendar

> Official public holidays of Türkiye (Law 2429 and Diyanet's religious holidays, 2022–2035) and business-day arithmetic.

- Business days are Monday–Friday minus official holidays. The eves of Republic Day (28 Oct) and the religious holidays are half days: a holiday from 13:00.
- `half_days`: `working` (default) or `holiday`.
- `calendar`: `standard` (default), `public_sector` (also excludes announced administrative leave, from 2026) or `tcmb` (days the central bank publishes rates; no bulletin on eves).

## REST endpoints

- [Holidays of a year](https://foster-mcp.esakiz.workers.dev/v1/calendar/holidays?year=2027)
- [Is a date a business day?](https://foster-mcp.esakiz.workers.dev/v1/calendar/day?date=2026-10-28)
- [Add business days](https://foster-mcp.esakiz.workers.dev/v1/calendar/add?date=2026-10-23&days=10): the start date is not counted; negative days go back
- [Count business days](https://foster-mcp.esakiz.workers.dev/v1/calendar/count?from=2026-10-01&to=2026-10-31): both ends included

## MCP

Remote MCP server (Streamable HTTP): https://foster-mcp.esakiz.workers.dev/calendar/mcp
Tools: list_holidays, check_business_day, add_business_days, count_business_days.

# Turkish identifier validation

> Checksum validation of Turkish IBANs, tax numbers (VKN) and national ID numbers (TCKN). Format only: a valid result does not prove the number is registered. Inputs are never stored or logged; the national ID is not echoed back.

## REST endpoints (POST, JSON body)

- https://foster-mcp.esakiz.workers.dev/v1/validate/iban with {"iban": "TR33 0006 1005 1978 6457 8413 26"}: returns the bank code and grouped form
- https://foster-mcp.esakiz.workers.dev/v1/validate/tax-number with {"vkn": "4540536920"}
- https://foster-mcp.esakiz.workers.dev/v1/validate/national-id with {"tckn": "10000000146"}

## MCP

Remote MCP server (Streamable HTTP): https://foster-mcp.esakiz.workers.dev/validate/mcp
Tools: validate_iban, validate_tax_number, validate_national_id.