Realtime Exchange Rate MCP Server

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Give your AI coding assistant a live window into the foreign-exchange market.

A Model Context Protocol server that lets Claude Code, Cursor, Claude Desktop, Windsurf, and any other MCP-compatible client fetch real-time currency rates, historical data, and multi-currency lookups.

After installation, your assistant can answer questions like:

• "What's the current USD to EUR rate?"
• "Show me how GBP/JPY moved over the last 30 days."
• "Convert 250 USD into CAD at a real rate."
• "Compare USD against EUR, GBP, and JPY simultaneously."
• "List every supported currency."

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Table of contents

• What you get
• Get an API key (required)
• Install
• Quick setup per client
  • Claude Code
  • Cursor
  • Claude Desktop
  • Windsurf
  • Generic stdio MCP client
• Verify it works
• Tools reference
• Environment variables
• Troubleshooting
• Error reference
• FAQ
• Development
• Changelog
• Support
• License

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What you get

Capability	Detail
Currencies	150+ ISO 4217 codes, all major and most exotics
Update frequency	Mid-market rates refresh every ~60 seconds
Historical depth	Up to 1 year via 1d / 7d / 30d / 1y granularity
Tools exposed	4 — get_exchange_rate, get_historical_rates, get_rates_authenticated, list_currencies
Transport	stdio (subprocess), MCP 1.x compatible
Runtime	Node.js ≥18

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Get an API key (required)

The server will not start without a valid ALLRATES_API_KEY. Rates are served by AllRatesToday; a free key is enough for development and personal use.

1. Register at allratestoday.com/register
2. Verify your email
3. Copy your key from the dashboard (format: art_live_xxxxx)
4. Use it as ALLRATES_API_KEY in the configs below

If the key is missing, the server prints clear registration instructions on stderr and exits with code 1.

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Install

The server is published as an npm package. The simplest install is zero-install via npx, which is what every config below uses.

# Run without installing (recommended)
npx -y @allratestoday/mcp-server

# Or install globally
npm install -g @allratestoday/mcp-server
allratestoday-mcp

Both commands launch the stdio MCP server and wait for a client to connect. They're not meant to be run directly from your shell — your MCP client launches them as a subprocess.

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Quick setup per client

Each client reads MCP servers from a different config file. Pick yours below.

Claude Code

The fastest path uses the built-in CLI:

claude mcp add allratestoday -- npx -y @allratestoday/mcp-server
claude mcp env allratestoday ALLRATES_API_KEY=art_live_xxxxx

Restart Claude Code. Verify by asking it: "What's the current USD to EUR rate?"

Cursor

Edit ~/.cursor/mcp.json (or .cursor/mcp.json inside your project for project-scoped servers):

{
  "mcpServers": {
    "allratestoday": {
      "command": "npx",
      "args": ["-y", "@allratestoday/mcp-server"],
      "env": {
        "ALLRATES_API_KEY": "art_live_xxxxx"
      }
    }
  }
}

Restart Cursor. The four tools should appear in the MCP tool picker.

Claude Desktop

Edit the config file (path depends on OS):

OS	Path
macOS	~/Library/Application Support/Claude/claude_desktop_config.json
Windows	%APPDATA%\Claude\claude_desktop_config.json
Linux	~/.config/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "allratestoday": {
      "command": "npx",
      "args": ["-y", "@allratestoday/mcp-server"],
      "env": {
        "ALLRATES_API_KEY": "art_live_xxxxx"
      }
    }
  }
}

Fully quit and reopen Claude Desktop (Cmd+Q on macOS, right-click tray icon → Exit on Windows). Closing the window alone keeps the old config loaded.

Windsurf

Edit ~/.codeium/windsurf/mcp_config.json:

{
  "mcpServers": {
    "allratestoday": {
      "command": "npx",
      "args": ["-y", "@allratestoday/mcp-server"],
      "env": {
        "ALLRATES_API_KEY": "art_live_xxxxx"
      }
    }
  }
}

Restart Windsurf.

Generic stdio MCP client

Any MCP host that supports stdio transport works. The launch command is:

npx -y @allratestoday/mcp-server

…with the environment variable ALLRATES_API_KEY set. The protocol version is MCP 1.x.

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Verify it works

After configuring your client, test in this order:

1. Server starts — open the client. If the MCP integration shows a red dot or "failed to connect", the API key is missing or wrong (see Troubleshooting).

2. Tools are listed — most clients have a "tools" or "MCP" panel. You should see:

   • get_exchange_rate
   • get_historical_rates
   • get_rates_authenticated
   • list_currencies

3. A live call returns a number — ask the assistant:

   What's the current USD to EUR rate?

   The assistant will call get_exchange_rate(source: "USD", target: "EUR") and reply with a real rate (e.g. "USD to EUR is currently 0.9214."). If it fabricates a number without making a tool call, the server isn't connected.

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Tools reference

All four tools require an API key.

get_exchange_rate

Current mid-market rate between two currencies.

Input

Field	Type	Required	Description
source	string	yes	3-letter ISO 4217 code, e.g. USD
target	string	yes	3-letter ISO 4217 code, e.g. EUR

Example call

{ "source": "USD", "target": "EUR" }

Example response

{ "rate": 0.92145, "source": "wise" }

get_historical_rates

Time-series data points for a currency pair over a fixed period.

Input

Field	Type	Required	Description
source	string	yes	Source currency code
target	string	yes	Target currency code
period	string	no (default 7d)	One of 1d, 7d, 30d, 1y

Granularity by period

period	Data points
1d	Hourly (24 points)
7d	Daily (7 points)
30d	Daily (30 points)
1y	Weekly (52 points)

Example call

{ "source": "USD", "target": "INR", "period": "30d" }

Example response (truncated)

{
  "source": "USD",
  "target": "INR",
  "period": "30d",
  "data": [
    { "date": "2026-03-27T00:00:00Z", "rate": 83.42, "timestamp": 1743033600000 },
    { "date": "2026-03-28T00:00:00Z", "rate": 83.51, "timestamp": 1743120000000 },
    "..."
  ]
}

get_rates_authenticated

Multiple targets in one call, with optional historical timestamp or grouping window.

Input

Field	Type	Required	Description
source	string	yes	Source currency code
target	string	yes	One or more codes, comma-separated (EUR,GBP,JPY)
time	string (ISO 8601)	no	Historical point in time
group	string	no	One of hour, day, week, month

Example call

{ "source": "USD", "target": "EUR,GBP,JPY" }

Example response

[
  { "rate": 0.9214, "source": "USD", "target": "EUR", "time": "2026-04-26T11:00:00Z" },
  { "rate": 0.7891, "source": "USD", "target": "GBP", "time": "2026-04-26T11:00:00Z" },
  { "rate": 151.34, "source": "USD", "target": "JPY", "time": "2026-04-26T11:00:00Z" }
]

list_currencies

All supported currencies with codes, names, and symbols. Cached upstream for 24 hours.

Input — none.

Example response (truncated)

{
  "currencies": [
    { "code": "USD", "name": "US Dollar", "symbol": "$" },
    { "code": "EUR", "name": "Euro", "symbol": "€" },
    { "code": "GBP", "name": "British Pound", "symbol": "£" },
    "..."
  ],
  "count": 162
}

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Environment variables

Variable	Default	Required	Purpose
ALLRATES_API_KEY	—	yes	Your API key. The server exits at startup if unset.
ALLRATES_BASE_URL	https://allratestoday.com/api	no	Override for self-hosted or staging deployments.

You set these in your MCP client's config (in the env block) — not in your shell — because MCP servers are launched as subprocesses with isolated environments.

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Troubleshooting

Symptom	Likely cause	Fix
Client shows "MCP server failed to start" or red dot	ALLRATES_API_KEY not set or invalid	Verify the key in your client config; check it matches the dashboard
Tools show but every call returns "Invalid API key"	Key is malformed (missing prefix, truncated, or revoked)	Copy a fresh key from the dashboard
Tools return "API quota exceeded"	Plan request limit hit	Wait until next month or upgrade plan
Historical tool returns "Bad request"	Invalid period or unknown currency code	Period must be 1d/7d/30d/1y; codes must be 3 letters
Server starts but tools never appear in client	Client didn't reload after config change	Fully quit (not just close) and reopen the client
npx runs but hangs forever	The server is waiting for an MCP client to connect — this is normal when run from a shell	Don't run from a shell; let your MCP client launch it

Inspect server logs

To see what the server is doing, run it manually with the API key set:

ALLRATES_API_KEY=art_live_xxxxx npx -y @allratestoday/mcp-server

You should see no output when healthy (stdio is reserved for the MCP protocol). Any errors print to stderr.

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Error reference

The server maps API errors to clear, actionable messages.

HTTP status	Meaning	Tool error message
200	Success	(rate returned)
400	Bad request — usually unknown currency code	Bad request — possibly an unknown currency code
401	Invalid or missing API key	Invalid API key
429	Quota exceeded	API quota exceeded
5xx	Upstream server-side issue	HTTP 5xx — <upstream message>

The LLM will surface these messages in its response, so a user prompt that hits a 429 results in the assistant saying "the API quota has been exceeded — please try again next month or upgrade your plan."

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FAQ

Do you store my conversation or query data? No. Only your API key and the request parameters (source, target, period, time) are sent to the upstream API — never the LLM's conversation context, sheet contents, or anything else.

What happens to my API key? It's only sent as a Bearer token in the Authorization header on requests to the upstream API. It's never logged or transmitted elsewhere.

Why is my historical request slow on first call? Cold-start of npx (first run downloads the package) plus an initial upstream cache miss. Subsequent calls are fast (<200ms typically).

Can I run this without npm/Node? Not currently — Node ≥18 is required. We've considered a standalone binary; if that matters to you, open an issue.

Is there a self-hosted option? Yes, set ALLRATES_BASE_URL to point to your own instance.

Does this work with ChatGPT? The Anthropic MCP standard works with any MCP-compatible client. ChatGPT Desktop has experimental MCP support; check OpenAI's docs for current status.

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Development

git clone https://github.com/cahthuranag/realtime-exchange-rate-mcp.git
cd realtime-exchange-rate-mcp
npm install
npm run build
ALLRATES_API_KEY=art_live_xxxxx node dist/index.js

The server runs on stdio and waits for an MCP client to connect. Hit Ctrl+C to exit.

To watch and rebuild on changes during development:

npm run dev

To test against a local instance:

ALLRATES_BASE_URL=http://localhost:8080/api ALLRATES_API_KEY=test_key node dist/index.js

Project structure

src/
├── index.ts      # MCP server, tool registration, request handlers
└── client.ts     # HTTP client + error mapping
dist/             # Compiled JS (gitignored)
server.json       # MCP registry manifest
package.json      # npm metadata, dependencies, scripts

Contributing

Issues and PRs welcome at github.com/cahthuranag/realtime-exchange-rate-mcp. Before opening a PR:

1. npm run build should succeed with no errors
2. Test against a real API key (set in ALLRATES_API_KEY)
3. Update tool descriptions in src/index.ts if you change tool behavior
4. Update this README's "Tools reference" section if you add or rename a tool

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Changelog

See GitHub Releases for the full list. Recent highlights:

• 0.3.x — API key required for all tools; fail-fast at startup with clear error
• 0.2.x — Removed news tool, required auth on get_historical_rates
• 0.1.x — Initial release with 5 tools

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Support

• Bug reports: github.com/cahthuranag/realtime-exchange-rate-mcp/issues
• MCP questions: modelcontextprotocol.io — protocol docs

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License

MIT — see LICENSE.