@cyanheads/exchange-rates-mcp-server
by cyanheads
README.md
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<h1>@cyanheads/exchange-rates-mcp-server</h1>
<p><b>Convert currencies, get FX rates, and query historical ECB exchange rate data via MCP. STDIO or Streamable HTTP.</b>
<div>7 Tools • 1 Opt-in Tool • 2 Resources</div>
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[](./CHANGELOG.md) [](./LICENSE) [](https://github.com/users/cyanheads/packages/container/package/exchange-rates-mcp-server) [](https://modelcontextprotocol.io/) [](https://www.npmjs.com/package/@cyanheads/exchange-rates-mcp-server) [](https://www.typescriptlang.org/) [](https://bun.sh/)
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[](https://github.com/cyanheads/exchange-rates-mcp-server/releases/latest/download/exchange-rates-mcp-server.mcpb) [](https://cursor.com/en/install-mcp?name=exchange-rates-mcp-server&config=eyJjb21tYW5kIjoibnB4IiwiYXJncyI6WyIteSIsIkBjeWFuaGVhZHMvZXhjaGFuZ2UtcmF0ZXMtbWNwLXNlcnZlciJdfQ==) [](https://vscode.dev/redirect?url=vscode:mcp/install?%7B%22name%22%3A%22exchange-rates-mcp-server%22%2C%22command%22%3A%22npx%22%2C%22args%22%3A%5B%22-y%22%2C%22%40cyanheads%2Fexchange-rates-mcp-server%22%5D%7D)
[](https://www.npmjs.com/package/@cyanheads/mcp-ts-core)
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**Public Hosted Server:** [https://exchange-rates.caseyjhand.com/mcp](https://exchange-rates.caseyjhand.com/mcp)
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---
## Overview
ECB reference exchange rates via Frankfurter — a keyless proxy covering ~30 currencies back to 1999-01-04. Convert amounts, disambiguate currency codes, and pull point-in-time or historical rates from any MCP client, with SQL analytics over long time-series when DataCanvas is enabled. Runs as a stdio process, a local Streamable HTTP server, or the public hosted endpoint above.
### Tools
| Tool | Description |
|:---|:---|
| `fx_list_currencies` | List all ~30 ECB-supported ISO 4217 currencies with full names |
| `fx_get_rates` | Snapshot of all rates for a base currency at latest or a historical date |
| `fx_get_rate` | Exchange rate for a single currency pair at latest or a historical date |
| `fx_convert_currency` | Convert an amount between two currencies at latest or a historical rate |
| `fx_get_timeseries` | Historical daily rates for a currency pair over a date range |
| `fx_dataframe_describe` | List DataCanvas tables and columns staged by a prior `fx_get_timeseries` call |
| `fx_dataframe_query` | Run a read-only SQL SELECT against a staged DataCanvas table |
| `fx_dataframe_drop` | Remove one staged DataCanvas table or view (opt-in, destructive) |
The three `fx_dataframe_*` tools need `CANVAS_PROVIDER_TYPE=duckdb` — unset, they're not advertised in `tools/list` at all, and `fx_get_timeseries` returns every range inline instead. `fx_dataframe_drop` additionally needs `FX_ENABLE_CANVAS_DROP=true`.
### Resources
| Resource | Description |
|:---|:---|
| `fx://currencies` | All supported currencies as a stable reference document |
| `fx://rates/latest/{base}` | Latest rates snapshot for a base currency as a stable URI |
All resource data is also reachable via tools — use `fx_list_currencies` or `fx_get_rates` for programmatic access.
## Capability reference
### `fx_list_currencies` <sub>tool</sub>
- No input parameters
- Returns `[{ code, name }]` for all ~30 ECB-scoped currencies, sorted alphabetically by code
- ECB coverage shifts as currencies enter or exit scope — call this to validate a user-supplied code rather than hard-coding a list
---
### `fx_get_rates` <sub>tool</sub>
- `base_currency` required; `date` optional (default latest, ECB data from 1999-01-04, no future dates); optional `symbols` array narrows the response and must name at least one code
- Returns a `rates` map (quote code → rate), the actual `rate_date`, and `date_snapped: true` when a weekend/holiday request snapped to the prior business day
- Naming the base currency in `symbols` is valid — answered locally with a rate of 1 rather than sent upstream
- Typed failures: `invalid_date_format`, `unsupported_currency`, `date_out_of_range`, `upstream_no_data`
---
### `fx_get_rate` <sub>tool</sub>
- `base_currency`, `quote_currency` required; `date` optional (default latest, ECB data from 1999-01-04, no future dates)
- Returns `rate`, `rate_date`, and `date_snapped: true` when a weekend/holiday request snapped to the prior business day
- Cross-rates (neither side EUR) triangulate through EUR in one upstream call; a same-currency pair returns a rate of 1 without reaching the API, still dated to the real publication day
- Typed failures: `invalid_date_format`, `unsupported_currency`, `date_out_of_range`, `upstream_no_data`
---
### `fx_convert_currency` <sub>tool</sub>
- `base_currency`, `quote_currency`, `amount` (must be > 0) required; `date` optional (default latest, ECB data from 1999-01-04, no future dates)
- Handles EUR↔any, any↔EUR, and cross-rate pairs (e.g. USD→JPY) in a single upstream call
- Returns `quote_amount` (rounded to 6 decimal places), `rate`, `rate_date`, `date_snapped`, plus `rate_type` and `source` provenance
- Typed failures: `invalid_date_format`, `unsupported_currency`, `date_out_of_range`, `upstream_no_data`
---
### `fx_get_timeseries` <sub>tool</sub>
- `base_currency`, `quote_currency`, `start_date`, `end_date` required (ECB data from 1999-01-04, no future dates, start ≤ end); optional `canvas_id` appends to an existing canvas
- Inline results page at 500 publication days — `rate_count` is always the range total; `truncated: true` plus `next_start_date` continue the page
- Ranges over `FX_TIMESERIES_CANVAS_THRESHOLD_DAYS` (default 90 days) spill to DataCanvas when configured — response carries `spilled: true`, `canvas_id`, `table_name`; without DataCanvas they're paged inline instead
- A same-currency pair returns a rate of 1 on each real ECB publication day in range, not a synthetic Mon–Fri loop
- An empty range (only weekends/holidays) returns `rate_count: 0` with an explanatory `notice`, distinguishable from an error
---
### `fx_dataframe_describe` <sub>tool</sub>
- `canvas_id` required (from a prior `fx_get_timeseries` call)
- Returns each staged table's `kind`, `row_count`, and column schema (`name`, `type`, `nullable`), plus `expires_at`
- Required first step before `fx_dataframe_query`; needs `CANVAS_PROVIDER_TYPE=duckdb` — unregistered otherwise
- `canvas_not_found` when the ID doesn't exist or has expired
---
### `fx_dataframe_query` <sub>tool</sub>
- `canvas_id` and a read-only SQL `query` required; `row_limit` optional (1–10,000, default 150)
- Supports aggregations, GROUP BY, window functions, and JOINs across tables from multiple `fx_get_timeseries` calls
- Returns at most `row_limit` rows; `truncated: true` plus a `notice` give the `ORDER BY <column> LIMIT <n> OFFSET <m>` shape for the next page — ORDER BY is required for stable paging
- Markdown table cells are escaped so pipes, angle brackets, and line breaks stay inside their cell; `structuredContent` keeps raw values
- Needs `CANVAS_PROVIDER_TYPE=duckdb`; typed failures: `canvas_not_found`, `missing_table`, `invalid_query`
---
### `fx_dataframe_drop` <sub>tool</sub>
- `canvas_id` and exact `table_name` (from `fx_dataframe_describe`) required
- Removes one staged table or view; ECB rate data is untouched and the series can be re-staged via `fx_get_timeseries`
- Returns `dropped: true`/`false` depending on whether the table existed
- Disabled unless `FX_ENABLE_CANVAS_DROP=true` — listed with its enable hint but uncallable otherwise; also needs `CANVAS_PROVIDER_TYPE=duckdb`
---
### `fx://currencies` <sub>resource</sub>
- No parameters; returns `currencies`, `count`, `source` as `application/json` — the same payload as `fx_list_currencies`
- Listed as a single static resource
---
### `fx://rates/latest/{base}` <sub>resource</sub>
- `base` is an ISO 4217 currency code in the URI
- Returns `base_currency`, `rate_date`, a `rates` map, `rate_type`, and `source` for the latest ECB fix
- Listed with four sample URIs (EUR, USD, GBP, JPY) as discovery hints
## Features
Built on [`@cyanheads/mcp-ts-core`](https://github.com/cyanheads/mcp-ts-core): stdio and Streamable HTTP transports, pluggable auth (`none` / `jwt` / `oauth`), swappable storage (`in-memory`, `filesystem`, `Supabase`, `Cloudflare KV/R2/D1`), structured logging with optional OpenTelemetry tracing.
ECB-specific:
- Keyless access via [Frankfurter](https://www.frankfurter.dev/) — a Cloudflare-fronted ECB proxy; no API keys required
- Cross-rate triangulation: any pair works — USD → JPY is one upstream call, cross-rated through EUR on Frankfurter's side
- Weekend/holiday date semantics: `date_snapped` surfaces when the API returns a different date than requested
- Identity pairs never reach the upstream API: a currency against itself returns a rate of 1, dated to the day the ECB actually published for that currency rather than to the calendar date requested
- Long time-series spill to DataCanvas (DuckDB) when enabled, for SQL aggregation over the full range
Agent-friendly output:
- Rate provenance on every response — `rate_type`, `source`, `rate_date`, and `date_snapped` so agents can reason about trust and freshness
- Structured error contracts — typed `reason` fields (`unsupported_currency`, `date_out_of_range`, `invalid_query`, …) let callers branch on failure type, not string parsing
- Bounded responses — inline time-series pages continue from `next_start_date`, and SQL results cap at `row_limit`, so no call returns an unbounded payload
- Success-path `notice` enrichment — explains an empty series, where to continue a paged series, or which tools read a staged one, so a legitimate zero-result never reads as a failure
---
## Getting started
### Public Hosted Instance
A public instance is available at `https://exchange-rates.caseyjhand.com/mcp` — no installation required. Point any MCP client at it via Streamable HTTP:
```json
{
"mcpServers": {
"exchange-rates-mcp-server": {
"type": "streamable-http",
"url": "https://exchange-rates.caseyjhand.com/mcp"
}
}
}
```
### Self-Hosted / Local
No API key required — Frankfurter is keyless. Add the following to your MCP client configuration file:
```json
{
"mcpServers": {
"exchange-rates-mcp-server": {
"type": "stdio",
"command": "bunx",
"args": ["@cyanheads/exchange-rates-mcp-server@latest"],
"env": {
"MCP_TRANSPORT_TYPE": "stdio",
"MCP_LOG_LEVEL": "info"
}
}
}
}
```
Or with npx (no Bun required):
```json
{
"mcpServers": {
"exchange-rates-mcp-server": {
"type": "stdio",
"command": "npx",
"args": ["-y", "@cyanheads/exchange-rates-mcp-server@latest"],
"env": {
"MCP_TRANSPORT_TYPE": "stdio",
"MCP_LOG_LEVEL": "info"
}
}
}
}
```
Or with Docker:
```json
{
"mcpServers": {
"exchange-rates-mcp-server": {
"type": "stdio",
"command": "docker",
"args": [
"run", "-i", "--rm",
"-e", "MCP_TRANSPORT_TYPE=stdio",
"ghcr.io/cyanheads/exchange-rates-mcp-server:latest"
]
}
}
}
```
To enable DataCanvas for long time-series SQL analytics — which also registers `fx_dataframe_describe` and `fx_dataframe_query`, skipped from `tools/list` otherwise — add `CANVAS_PROVIDER_TYPE=duckdb`:
```json
{
"mcpServers": {
"exchange-rates-mcp-server": {
"type": "stdio",
"command": "bunx",
"args": ["@cyanheads/exchange-rates-mcp-server@latest"],
"env": {
"MCP_TRANSPORT_TYPE": "stdio",
"CANVAS_PROVIDER_TYPE": "duckdb"
}
}
}
}
```
For Streamable HTTP, set the transport and start the server:
```sh
MCP_TRANSPORT_TYPE=http MCP_HTTP_PORT=3010 bun run start:http
# Server listens at http://localhost:3010/mcp
```
### Prerequisites
- [Bun v1.4.0](https://bun.sh/) or higher (or Node.js v24+).
- No API key — Frankfurter is free and keyless.
### Installation
1. **Clone the repository:**
```sh
git clone https://github.com/cyanheads/exchange-rates-mcp-server.git
```
2. **Navigate into the directory:**
```sh
cd exchange-rates-mcp-server
```
3. **Install dependencies:**
```sh
bun install
```
4. **Configure environment:**
```sh
cp .env.example .env
# edit .env as needed (all vars are optional — no keys required)
```
---
## Configuration
All configuration is validated at startup via Zod schemas. Environment variables:
| Variable | Description | Default |
|:---------|:------------|:--------|
| `FRANKFURTER_BASE_URL` | Frankfurter API base URL. Override for local testing or a self-hosted instance. | `https://api.frankfurter.dev/v1` |
| `FX_TIMESERIES_CANVAS_THRESHOLD_DAYS` | Day range above which `fx_get_timeseries` spills to DataCanvas, when one is configured. | `90` |
| `FX_ENABLE_CANVAS_DROP` | Enable the destructive `fx_dataframe_drop` tool. Off by default: the tool stays listed with its enable hint but is uncallable. | `false` |
| `CANVAS_PROVIDER_TYPE` | Canvas engine. Set to `duckdb` to enable DataCanvas for `fx_get_timeseries` long-range spillover and to register the three `fx_dataframe_*` tools. At `none` they are skipped from `tools/list`. | `none` |
| `MCP_TRANSPORT_TYPE` | Transport: `stdio` or `http`. | `stdio` |
| `MCP_HTTP_PORT` | Port for HTTP server. | `3010` |
| `MCP_SESSION_MODE` | HTTP session mode: `auto`, `stateful`, or `stateless`. The server declares `stateless` in code — no handler here asks the client for input mid-call, so nothing needs a session to resume — and setting this variable overrides that declaration. | `stateless` |
| `MCP_AUTH_MODE` | Auth mode: `none`, `jwt`, or `oauth`. | `none` |
| `MCP_LOG_LEVEL` | Log level (RFC 5424: `debug`, `info`, `notice`, `warning`, `error`). | `info` |
| `OTEL_ENABLED` | Enable [OpenTelemetry instrumentation](https://github.com/cyanheads/mcp-ts-core/tree/main/docs/telemetry). | `false` |
See [`.env.example`](./.env.example) for the full list of optional overrides including storage, session, and telemetry vars.
---
## Running the server
### Local development
- **Build and run:**
```sh
bun run rebuild
bun run start:stdio
# or
bun run start:http
```
- **Run checks and tests:**
```sh
bun run devcheck # Lint, format, typecheck, security, changelog sync
bun run test # Vitest test suite
bun run lint:mcp # Validate MCP definitions against spec
```
### Docker
```sh
docker build -t exchange-rates-mcp-server .
docker run --rm -p 3010:3010 exchange-rates-mcp-server
```
The Dockerfile defaults to HTTP transport, stateless session mode, and logs to `/var/log/exchange-rates-mcp-server`. OpenTelemetry peer dependencies are installed by default — build with `--build-arg OTEL_ENABLED=false` to omit them. DuckDB native binaries are pre-built in the build stage and copied to production, keeping the production image free of build tools.
---
## Project structure
| Directory | Purpose |
|:----------|:--------|
| `src/index.ts` | `createApp()` entry point — registers tools, resources, and canvas accessor. |
| `src/config/` | Server-specific environment variable parsing and validation with Zod. |
| `src/mcp-server/tools/` | Tool definitions (`*.tool.ts`) — `fx_*` tools. |
| `src/mcp-server/resources/` | Resource definitions — `fx://currencies` and `fx://rates/latest/{base}`. |
| `src/services/frankfurter/` | Frankfurter HTTP client, retry logic, and domain types. |
| `src/services/canvas/` | Module-level DataCanvas accessor for `fx_get_timeseries` spillover. |
| `src/utils/` | Output helpers — Markdown table-cell escaping for `fx_dataframe_query`. |
| `tests/` | Unit and integration tests mirroring `src/`. |
| `docs/` | Design document and idea notes. |
---
## Development guide
See [`CLAUDE.md`](./CLAUDE.md) for development guidelines and architectural rules. The short version:
- Handlers throw, framework catches — no `try/catch` in tool logic
- Use `ctx.log` for request-scoped logging, `ctx.state` for tenant-scoped storage
- Register new tools and resources via the barrels in `src/mcp-server/*/definitions/index.ts`
- Wrap external API calls: validate raw → normalize to domain type → return output schema; never fabricate missing fields
- ECB rates are mid-market reference rates — preserve the `rate_type` provenance in every response
---
## Contributing
Issues are welcome. Run checks and tests before submitting:
```sh
bun run devcheck
bun run test
```
---
## License
Apache-2.0 — see [LICENSE](LICENSE) for details.
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