@cyanheads/reference-data-mcp-server
by cyanheads
README.md
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<h1>@cyanheads/reference-data-mcp-server</h1>
<p><b>Look up countries, timezones, periodic table elements, physical constants, units, HTTP status codes, and MIME types via MCP. STDIO or Streamable HTTP.</b>
<div>10 Tools • 3 Resources</div>
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[](./CHANGELOG.md) [](./LICENSE) [](https://github.com/users/cyanheads/packages/container/package/reference-data-mcp-server) [](https://modelcontextprotocol.io/) [](https://www.npmjs.com/package/@cyanheads/reference-data-mcp-server) [](https://www.typescriptlang.org/) [](https://bun.sh/)
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[](https://github.com/cyanheads/reference-data-mcp-server/releases/latest/download/reference-data-mcp-server.mcpb) [](https://cursor.com/en/install-mcp?name=reference-data-mcp-server&config=eyJjb21tYW5kIjoibnB4IiwiYXJncyI6WyIteSIsIkBjeWFuaGVhZHMvcmVmZXJlbmNlLWRhdGEtbWNwLXNlcnZlciJdfQ==) [](https://vscode.dev/redirect?url=vscode:mcp/install?%7B%22name%22%3A%22reference-data-mcp-server%22%2C%22command%22%3A%22npx%22%2C%22args%22%3A%5B%22-y%22%2C%22%40cyanheads%2Freference-data-mcp-server%22%5D%7D)
[](https://www.npmjs.com/package/@cyanheads/mcp-ts-core)
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**Public Hosted Server:** [https://reference-data.caseyjhand.com/mcp](https://reference-data.caseyjhand.com/mcp)
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---
## Overview
Countries, timezones, periodic table elements, physical constants, units, HTTP status codes, and MIME types — all served from static, in-memory datasets, entirely offline with no API keys or rate limits. Look up, search, and convert across these domains from any MCP client. Runs as a stdio process, a local Streamable HTTP server, or the public hosted endpoint above.
### Tools
| Tool | Description |
|:---|:---|
| `ref_geo_lookup` | Look up a country by name, ISO alpha-2, or alpha-3 code. |
| `ref_geo_search` | Search and filter countries by region, subregion, language, or currency. |
| `ref_timezone_lookup` | Get timezone info by IANA ID, country code, or city name. |
| `ref_timezone_convert` | Convert a local datetime from one timezone to another. |
| `ref_element_lookup` | Look up a periodic table element by name, symbol, or atomic number. |
| `ref_element_search` | Filter periodic table elements by category, group, period, or property range. |
| `ref_constant_lookup` | Look up a CODATA 2022 physical constant by name, symbol, or alias. |
| `ref_unit_convert` | Convert a numeric value between compatible units of measure. |
| `ref_http_status` | Look up an HTTP status code by number or keyword. |
| `ref_mime_type` | Look up a MIME type by type string or file extension. |
### Resources
| Resource | Description |
|:---|:---|
| `ref://countries/{alpha2}` | Full country record by ISO alpha-2 code. |
| `ref://elements/{number}` | Full element record by atomic number. |
| `ref://timezones/{iana_id}` | Timezone info by IANA ID (slashes percent-encoded as `%2F`). |
All resource data is also reachable via tools — use `ref_geo_lookup`, `ref_element_lookup`, and `ref_timezone_lookup` when you need flexible query modes or country search.
---
## Capability reference
### `ref_geo_lookup` <sub>tool</sub>
- Accepts fuzzy name matching ("Brasil" resolves to "Brazil"); a fuzzy hit adds an enrichment notice naming the canonical result
- Lookup modes: `auto` (alpha2 → alpha3 → name), `name`, `alpha2`, `alpha3`; numeric ISO codes are not supported
- Returns capital, region/subregion, languages, currencies, calling codes, TLD, flag emoji, and IANA timezone IDs
---
### `ref_geo_search` <sub>tool</sub>
- At least one filter required (`no_filters` error otherwise): keyword (name, native name, capital, subregion), region, subregion, language (ISO 639-1 code or name), or currency (ISO 4217 code or name)
- Limit 1–100 (default 20); `truncated` flag and `totalMatches` count when results are cut off
- Empty result set returns a notice echoing the applied filters
---
### `ref_timezone_lookup` <sub>tool</sub>
- Lookup modes: `auto` (IANA ID → country code → city name), `iana`, `country`; partial city matching ("Tokyo" → "Asia/Tokyo", "NY" → "America/New_York")
- Country-code queries return every timezone observed in that country
- Optional `at` (ISO 8601) evaluates DST state at a specific moment instead of now; malformed values raise `invalid_at`
- Returns current/standard UTC offsets, DST status and abbreviations, major cities, and country codes
---
### `ref_timezone_convert` <sub>tool</sub>
- `datetime` must be a local ISO 8601 string without an offset (regex-enforced, e.g. `2026-05-24T15:30:00`); `from_tz`/`to_tz` accept full IANA IDs or unambiguous city names
- Rejects out-of-range calendar dates and spring-forward DST gaps as `invalid_datetime`; unrecognized zones as `invalid_timezone`
- Returns source and target local datetimes with their respective UTC offsets, plus the UTC equivalent
---
### `ref_element_lookup` <sub>tool</sub>
- Lookup modes: `auto` (atomic number → symbol → name), `name`, `symbol`, `number`
- Full property set: atomic mass (`atomic_mass_estimated` flag), electron configuration, group/period/block, category, Pauling electronegativity, density, melting/boiling points in kelvin, phase at STP, radioactivity, natural occurrence, discovery data
- Data sourced from PubChem/IUPAC 2024; synthetic or unstable elements return `null` for experimentally inaccessible properties
---
### `ref_element_search` <sub>tool</sub>
- At least one filter required (`no_filters` error otherwise): category (partial match), group (1–18), period (1–7), atomic-number range, or atomic-mass range
- Valid categories: alkali metal, alkaline earth metal, transition metal, post-transition metal, metalloid, reactive nonmetal, noble gas, lanthanide, actinide
- Returns summaries (atomic number, symbol, name, mass, category) plus a `totalMatches` count and a notice when nothing matches
---
### `ref_constant_lookup` <sub>tool</sub>
- Fuzzy alias matching: "speed of light", "c", "Avogadro's number", "N_A", "Planck", "h", "Boltzmann", "k_B" all resolve against 32 CODATA 2022 constants
- `match_strategy` discriminates how the query resolved: `exact_symbol`, `exact_name`, or `fuzzy` (closest candidate — verify before reuse)
- Returns value, SI unit expression, absolute/relative uncertainty (`exact` flag for defined constants), CODATA identifier, and up to 3 related constants
---
### `ref_unit_convert` <sub>tool</sub>
- 11 measurement domains: length, mass, volume, temperature (non-linear C/F/K/R), speed, pressure, energy, power, frequency, digital storage, angle
- Mass `mt` is the metric tonne (1000 kg); `t` is the US short ton (907.18 kg) — distinct units, easily confused
- Typed errors: `incompatible_units` (mismatched quantities), `unknown_unit` (unrecognized abbreviation), `below_absolute_zero` (with the Kelvin equivalent)
---
### `ref_http_status` <sub>tool</sub>
- Numeric queries (e.g., "404") return an exact match; keyword queries (e.g., "not found", "too many requests") return the closest match plus alternatives
- Returns reason phrase, description, category (1xx–5xx), cacheability per RFC 9110, and the defining RFC with section reference
---
### `ref_mime_type` <sub>tool</sub>
- Accepts "image/webp", ".webp", or "webp" interchangeably
- Extension lookups return the canonical MIME type first; additional types sharing the extension are listed as alternatives
- Returns extensions, a compressibility flag (relevant for Content-Encoding decisions), and the data source (iana/apache/nginx)
---
### `ref://countries/{alpha2}` <sub>resource</sub>
- Full country record as `application/json` — same fields as `ref_geo_lookup`
- `alpha2` accepts either case; an unmatched code returns a `notFound` error
---
### `ref://elements/{number}` <sub>resource</sub>
- Full element record as `application/json` — same fields as `ref_element_lookup`
- `number` must be an integer string 1–118; out-of-range or unmatched values return `notFound`
---
### `ref://timezones/{iana_id}` <sub>resource</sub>
- Timezone record as `application/json` — same fields as `ref_timezone_lookup`, plus `evaluated_at`
- Slashes in the IANA ID must be percent-encoded as `%2F` (e.g. `America%2FNew_York`); an unencoded slash matches a separate catch-all that returns an actionable error with the correctly encoded URI
---
## 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.
Reference-data-specific:
- Entirely in-memory — all datasets load at startup; no runtime network calls, no API keys, no rate limits
- Works offline and in air-gapped environments
- Seven specialized services: geo (countries-list), timezone (Node.js Intl + @vvo/tzdb), elements (PubChem/IUPAC 2024, 118 elements), constants (CODATA 2022, 32 entries), units (convert-units), HTTP status (IANA registry), MIME types (mime-db, ~1,000 types)
Agent-friendly output:
- Structured error contracts on every tool — typed `reason` codes (`no_match`, `no_filters`, `unknown_unit`, `incompatible_units`, `below_absolute_zero`, `invalid_timezone`, `invalid_datetime`, `invalid_at`) with actionable recovery hints
- Discriminated outputs where relevant — `truncated` flag on search results, `alternatives` arrays on MIME/HTTP keyword matches, `atomic_mass_estimated` flag on element data, `match_strategy` on constant lookups
- Consistent `null` for genuinely unknown or inapplicable values rather than absent fields
---
## Getting started
### Public Hosted Instance
A public instance is available at `https://reference-data.caseyjhand.com/mcp` — no installation required. Point any MCP client at it via Streamable HTTP:
```json
{
"mcpServers": {
"reference-data-mcp-server": {
"type": "streamable-http",
"url": "https://reference-data.caseyjhand.com/mcp"
}
}
}
```
### Self-Hosted / Local
Add the following to your MCP client configuration file:
```json
{
"mcpServers": {
"reference-data-mcp-server": {
"type": "stdio",
"command": "bunx",
"args": ["@cyanheads/reference-data-mcp-server@latest"],
"env": {
"MCP_TRANSPORT_TYPE": "stdio",
"MCP_LOG_LEVEL": "info"
}
}
}
}
```
Or with npx (no Bun required):
```json
{
"mcpServers": {
"reference-data-mcp-server": {
"type": "stdio",
"command": "npx",
"args": ["-y", "@cyanheads/reference-data-mcp-server@latest"],
"env": {
"MCP_TRANSPORT_TYPE": "stdio",
"MCP_LOG_LEVEL": "info"
}
}
}
}
```
Or with Docker:
```json
{
"mcpServers": {
"reference-data-mcp-server": {
"type": "stdio",
"command": "docker",
"args": [
"run", "-i", "--rm",
"-e", "MCP_TRANSPORT_TYPE=stdio",
"ghcr.io/cyanheads/reference-data-mcp-server:latest"
]
}
}
}
```
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 keys required — this server is entirely self-contained.
### Installation
1. **Clone the repository:**
```sh
git clone https://github.com/cyanheads/reference-data-mcp-server.git
```
2. **Navigate into the directory:**
```sh
cd reference-data-mcp-server
```
3. **Install dependencies:**
```sh
bun install
```
4. **Configure environment (optional):**
```sh
cp .env.example .env
# edit .env if you want to override transport or logging defaults
```
---
## Configuration
No API keys are required. All configuration is optional overrides of framework defaults.
| Variable | Description | Default |
|:---------|:------------|:--------|
| `MCP_TRANSPORT_TYPE` | Transport: `stdio` or `http`. | `stdio` |
| `MCP_HTTP_PORT` | Port for HTTP server. | `3010` |
| `MCP_HTTP_HOST` | Host for HTTP server. | `127.0.0.1` |
| `MCP_SESSION_MODE` | Session mode: `stateful`, `stateless`, or `auto` (schema default `auto` resolves to stateful). | `stateless` |
| `MCP_AUTH_MODE` | Auth mode: `none`, `jwt`, or `oauth`. | `none` |
| `MCP_LOG_LEVEL` | Log level (RFC 5424): `debug`, `info`, `notice`, `warning`, `error`. | `info` |
| `LOGS_DIR` | Directory for log files (Node.js only). | `<project-root>/logs` |
| `OTEL_ENABLED` | Enable OpenTelemetry instrumentation (spans, metrics, completion logs). | `false` |
See [`.env.example`](./.env.example) for the full list of optional overrides.
---
## Running the server
### Local development
```sh
# One-time build
bun run rebuild
# Run the built server
bun run start:stdio
# or
bun run start:http
```
```sh
bun run devcheck # Lint, format, typecheck, security
bun run test # Vitest test suite
bun run lint:mcp # Validate MCP definitions against spec
```
### Docker
```sh
docker build -t reference-data-mcp-server .
docker run --rm -p 3010:3010 reference-data-mcp-server
```
The Dockerfile defaults to HTTP transport, stateless session mode, and logs to `/var/log/reference-data-mcp-server`. OpenTelemetry peer dependencies are installed by default — build with `--build-arg OTEL_ENABLED=false` to omit them.
---
## Project structure
| Directory | Purpose |
|:----------|:--------|
| `src/index.ts` | `createApp()` entry point — registers tools/resources and inits services. |
| `src/data/` | Static datasets (periodic table, physical constants, HTTP status codes). |
| `src/mcp-server/tools/` | Tool definitions (`*.tool.ts`). |
| `src/mcp-server/resources/` | Resource definitions (`*.resource.ts`). |
| `src/services/` | Domain service integrations (geo, timezone, elements, constants, units, http-status, mime). |
| `tests/` | Unit tests mirroring `src/`. |
| `docs/` | Generated docs (tree.md, design.md). |
| `changelog/` | Per-version changelog files. |
---
## 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 directly in `src/index.ts`
- Data integrity: validate raw → normalize to domain type → return output schema; never fabricate missing fields
---
## 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.
This server cannot be deployed
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