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io.github.cyanheads/exchange-rates-mcp-server

by cyanheads · remote · local (npm) · no sign-in to list tools · v0.5.0 · published by GitHub user cyanheads

Convert currencies, get FX rates, and query historical ECB exchange rate data.

Changes · 2
CompareRegistry entry

7 tools: 2 change things and 5 only read.

Scanned Oct 21, 2026

2 checks matched something in the tool definitions. No finding is not a safety guarantee. How the checks work.

claude mcp add --transport http exchange-rates https://exchange-rates.caseyjhand.com/mcp

Findings

Matches of fixed checks, with the text they matched.

2 warn
  • Warnfx_convert_currency

    The server marks "fx_convert_currency" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

    Matched text

    annotations: {"readOnlyHint":true,"idempotentHint":true,"openWorldHint":true}; The name "fx_convert_currency" says "convert": a word for a change.

    What this check looks for
  • Warnfx_dataframe_query

    The server marks "fx_dataframe_query" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

    Matched text

    annotations: {"readOnlyHint":true,"idempotentHint":true,"openWorldHint":false}; The name "fx_dataframe_query" says "query": a word for reading.

    What this check looks for

Tools

Open a tool for its reasons and full description. Descriptions are the publisher's own words, shown as they are.

7 tools

Changes things 2Claude Code: ask
  • fx_convert_currencyConvert an amount between any two currencies at the latest or a historical rate.1 finding

    Why it is in this group

    • The name "fx_convert_currency" says "convert": a word for a change.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.

    Findings

    • Warn

      The server marks "fx_convert_currency" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

      Matched text

      annotations: {"readOnlyHint":true,"idempotentHint":true,"openWorldHint":true}; The name "fx_convert_currency" says "convert": a word for a change.

      What this check looks for
    Description, as the server wrote it
    Convert an amount between any two currencies at the latest or a historical rate. Returns the converted amount, the rate used, the actual rate date, and whether the date was snapped from a weekend/holiday to the prior business day. Cross-rates are triangulated through EUR automatically.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: true
  • fx_dataframe_queryRun a read-only SQL SELECT against DataCanvas tables staged by fx_get_timeseries.1 finding

    Why it is in this group

    • The name "fx_dataframe_query" says "query": a word for reading.
    • The description's first verb is "run": a word for a change.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.

    Findings

    • Warn

      The server marks "fx_dataframe_query" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

      Matched text

      annotations: {"readOnlyHint":true,"idempotentHint":true,"openWorldHint":false}; The name "fx_dataframe_query" says "query": a word for reading.

      What this check looks for
    Description, as the server wrote it
    Run a read-only SQL SELECT against DataCanvas tables staged by fx_get_timeseries. Supports aggregations, GROUP BY, window functions, and JOINs across multiple registered tables. Run fx_dataframe_describe first to discover table names and column schemas. Requires DataCanvas, which is on by default — a deployment that turns it off does not list this tool at all, and fx_get_timeseries returns every range inline there.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: false
Only reads 5Claude Code: allow
  • fx_dataframe_describeList tables and columns staged on a DataCanvas from a prior fx_get_timeseries call.No findings

    Why it is in this group

    • The name "fx_dataframe_describe" says "describe": a word for reading.
    Description, as the server wrote it
    List tables and columns staged on a DataCanvas from a prior fx_get_timeseries call. Required first step before fx_dataframe_query — use it to discover table names and column schemas. Requires DataCanvas, which is on by default — a deployment that turns it off does not list this tool at all, and fx_get_timeseries returns every range inline there.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: false
  • fx_get_rateGet the exchange rate for a currency pair on a given date (default: latest).No findings

    Why it is in this group

    • The name "fx_get_rate" says "get": a word for reading.
    Description, as the server wrote it
    Get the exchange rate for a currency pair on a given date (default: latest). Returns the rate, the actual rate date (which may differ from the requested date on weekends/holidays — ECB publishes business days only), and source provenance. Cross-rates are triangulated through EUR automatically. A same-currency pair returns a rate of 1, dated to the same publication day any other pair would report for that date. Use fx_convert_currency when you want the converted amount; use this tool when you only need the rate number.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: true
  • fx_get_ratesGet all available exchange rates for one base currency in a single snapshot.No findings

    Why it is in this group

    • The name "fx_get_rates" says "get": a word for reading.
    Description, as the server wrote it
    Get all available exchange rates for one base currency in a single snapshot. Useful for bulk comparison and seeding downstream tools. Returns a map of quote currency → rate, the actual snapshot date, and whether a historical date was snapped from a weekend/holiday to the prior business day. Optionally filter to a subset of quote currencies via symbols. Listing the base currency itself in symbols is accepted and returns a rate of 1 for it.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: true
  • fx_get_timeseriesGet historical daily exchange rates for a currency pair over a date range.No findings

    Why it is in this group

    • The name "fx_get_timeseries" says "get": a word for reading.
    Description, as the server wrote it
    Get historical daily exchange rates for a currency pair over a date range. ECB publishes on business days only — weekends and holidays produce no entry, and no date outside the requested range is ever returned, so a range covering only non-publication days comes back with an empty rates map and a notice explaining why. A same-currency pair returns a rate of 1 on each publication day in the range. Inline results are returned as a date→rate map paged at 500 publication days: rate_count is always the total for the requested range, and when a page is cut short the response carries truncated=true and next_start_date — call again with start_date set to next_start_date and the same end_date for the next page. Long ranges (>90 days by default) are considered for DataCanvas staging: when the series exceeds the 40,000-character preview budget, it is staged and the response carries spilled=true, a canvas_id, and a table_name — call fx_dataframe_describe to inspect the staged table, then fx_dataframe_query to run SQL against it. On a deployment with DataCanvas turned off, long ranges are paged inline (spilled=false) and the notice says so.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: true
  • fx_list_currenciesList all supported ISO 4217 currency codes with their full names.No findings

    Why it is in this group

    • The name "fx_list_currencies" says "list": a word for reading.
    Description, as the server wrote it
    List all supported ISO 4217 currency codes with their full names. Call this before converting to disambiguate "dollars" (USD vs AUD vs CAD vs HKD vs SGD) or to validate a user-supplied currency code. Covers the ~30 ECB reference currencies.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: true

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Install

Pinned to version 0.5.0. Values in angle brackets are yours to fill in.

claude mcp add --transport http exchange-rates https://exchange-rates.caseyjhand.com/mcp

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json
{
  "permissions": {
    "allow": [
      "mcp__exchange-rates__fx_list_currencies",
      "mcp__exchange-rates__fx_get_rates",
      "mcp__exchange-rates__fx_get_rate",
      "mcp__exchange-rates__fx_get_timeseries",
      "mcp__exchange-rates__fx_dataframe_describe"
    ],
    "ask": [
      "mcp__exchange-rates__fx_convert_currency",
      "mcp__exchange-rates__fx_dataframe_query"
    ],
    "deny": []
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. It assumes the server is installed as exchange-rates. Review it before you use it.