@cyanheads/who-gho-mcp-server
Query WHO Global Health Observatory data — 3,102 indicators across 194 member states with country, region, year, and sex filters via MCP. STDIO or Streamable HTTP.
6 Tools • 4 Data Resources • 1 Skill
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**Public Hosted Server:** [https://who-gho.caseyjhand.com/mcp](https://who-gho.caseyjhand.com/mcp)
---
## Overview
Global health statistics from the WHO Global Health Observatory: 3,102 indicators across 194 member states. Search indicators and query data by country, region, income group, sex, and year.
### Tools
| Tool | Description |
|:---|:---|
| `who_search_indicators` | Search the GHO indicator catalog by keyword in indicator names |
| `who_list_indicators` | Browse the full indicator catalog with pagination |
| `who_get_indicator_metadata` | Fetch indicator names and dimension types, processing 10 codes per call with continuation for larger batches |
| `who_list_dimensions` | List all dimension type codes available in the GHO API |
| `who_list_dimension_values` | List valid codes and labels for a dimension type (COUNTRY, REGION, SEX, etc.) |
| `who_query_indicator_data` | Query data rows for an indicator with spatial, temporal, and dimension filters |
### Resources
| Resource | Description |
|:---|:---|
| `who://indicator/{indicatorCode}/metadata` | Indicator name and supported filter dimensions for a single code |
| `who://dimension/{dimensionCode}/values` | First 100 values for a dimension type |
| `who://dimension/{dimensionCode}/values{?limit,offset}` | One explicit page of a dimension type's values |
| `who://dimension/{dimensionCode}/values{?limit,offset,parentCode}` | One explicit page, narrowed to a parent code |
Each mirrors data also reachable via `who_get_indicator_metadata` and `who_list_dimension_values` — useful for clients that inject resources as context but don't call tools.
### Agent skill
[who-gho-guide](./skills/who-gho-guide/SKILL.md) covers dimension-position discovery, complete country comparisons, and countries versus regional aggregates. It ships with plugin installs, npm, Docker, and the MCPB bundle. MCP clients can discover its `SKILL.md` through `resources/list` or the `io.modelcontextprotocol/skills` extension (`skills/list`, `skills/get`, and `resources/directory/read`); the server also exposes the `skill://{+path}` resource template.
## Capability reference
### `who_search_indicators` tool
- Each whitespace-separated word must match a substring in the indicator name, in any order; no stemming or fuzzy expansion. If names have no matches, an exact indicator-code lookup is attempted.
- Returns indicator codes and display names for use with `who_query_indicator_data`
- Offset-based pagination (`offset`, default 0) with `limit` default 20, max 100; reports `totalCount`, `hasMore`, `pageInfo`, `nextOffset`
- An offset at or beyond `totalCount` returns an empty page; a `no_results` error is raised only when nothing matches at all
---
### `who_list_indicators` tool
- No keyword required — browse the 3,102-indicator catalog
- Offset-based pagination via `limit` (default 50, max 500) and `offset`
- Returns `totalCount` and `hasMore` for iteration
---
### `who_get_indicator_metadata` tool
- Accepts up to 1,000 indicator codes and processes the first 10 in parallel; submit returned `unprocessedCodes` next. With `GHO_CLAMP_LIMITS=false`, batches over 10 are rejected.
- Returns the full indicator name and supported dimension types (e.g. `COUNTRY`, `SEX`, `REGION`, `AGEGROUP`) for each resolved code
- Indicators with no dimension listing upstream return `dimensions: []` plus a `dimensionsNote` pointing at a sample data row's dimension type/value pairs. Metadata does not identify dimension positions.
- Codes resolving to neither a catalog entry nor dimension rows land in `notFound`; the call fails when no processed code resolves and no unprocessed codes remain
---
### `who_list_dimensions` tool
- No inputs — returns every dimension type code and human-readable title in the GHO catalog
- Common types: `COUNTRY`, `REGION`, `SEX`, `WORLDBANKINCOMEGROUP`, `AGEGROUP`
- Use to discover codes before calling `who_list_dimension_values`
---
### `who_list_dimension_values` tool
- Returns codes and labels for the dimension's values (e.g. the 234 country entries, the 43 WHO region codes), plus optional parent-hierarchy fields (`parentCode`, `parentLabel`, `parentDimension`)
- `parent_code` narrows hierarchical dimensions — `dimension: "COUNTRY"` with `parent_code: "EUR"` returns the 58 countries in the WHO European Region
- Deterministic ordering by `Code`; offset-based pagination (`offset`) with `limit` default 100, max 500 — `GHO` (3,103 values) and `DHSMICSGEOREGION` (4,932) need paging
- A `parent_code` that matches nothing returns an empty page for a known dimension; unknown dimensions fail even with a parent filter
- An unpaired UTF-16 surrogate in `dimension` fails as a typed `malformed_identifier` validation error
---
### `who_query_indicator_data` tool
- Spatial filters are mutually exclusive per call: `country_codes` (WHO country codes, including historical entries), `region_codes` (WHO aggregate rows), or `income_group_codes` (World Bank aggregate rows) — supplying more than one is a validation error
- `year_from` / `year_to` time range; `sex` (`SEX_BTSX`, `SEX_FMLE`, `SEX_MLE`) applies only when the indicator's first cross-cutting dimension is SEX. `dim1_value`, `dim2_value`, and `dim3_value` select observed positional values; discover positions from returned type/value pairs, not metadata. `sex` overrides `dim1_value` with a notice.
- `include_uncertainty` (default true) adds `low`/`high` bounds; `sort` (`year_desc` default or `year_asc`) with a total row ordering so paging never repeats or drops rows
- Offset-based pagination with `limit` default 200, max 1000; reports `totalRows`, `hasMore`, `pageInfo`, `nextOffset`
- Typed failure reasons: `indicator_not_found`, `no_data`, `ambiguous_spatial_filter`, `invalid_year_range`, `invalid_query`, `malformed_identifier`
---
### `who://indicator/{indicatorCode}/metadata` resource
- Indicator name and supported filter dimensions as `application/json`
- `indicatorCode` comes from `who_search_indicators` or `who_list_indicators`
- Empty `dimensions` carries a `dimensionsNote` when the upstream dimension table lists none for the code, rather than reporting a missing indicator
- Returns a 404 error only when the code resolves to neither a catalog name nor any dimension rows
---
### `who://dimension/{dimensionCode}/values` resource
- Bare URI returns the first 100 values for the dimension (`dimensionCode` from `who_list_dimensions`), as `application/json`
- Registered separately from the two paged variants below because the MCP SDK's RFC 6570 matcher treats every URI query variable as required — one template cannot serve both a bare and a paged form
- An unfiltered empty result means the dimension code does not exist
---
### `who://dimension/{dimensionCode}/values{?limit,offset}` resource
- `limit` (1–500) and `offset` must both be present in the URI — the query variables are required, not optional
- Same page fields as the bare URI: `totalCount`, `hasMore`, `nextOffset`, and an optional `notice`
- An offset at or beyond `totalCount` returns an empty page, not an error
---
### `who://dimension/{dimensionCode}/values{?limit,offset,parentCode}` resource
- Adds `parentCode` to narrow to one parent value, e.g. `parentCode="EUR"` for countries in the WHO European Region; `limit`, `offset`, and `parentCode` must all be present in the URI
- A `parentCode` that matches nothing returns an empty page for a known dimension; unknown dimensions fail even with a parent filter
- Same output shape as the bare and paged resources: `dimension`, `values`, `totalCount`, `hasMore`, `nextOffset`, `notice`
## 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.
WHO GHO-specific:
- Full coverage of the [WHO GHO OData API v2](https://www.who.int/data/gho/info/gho-odata-api) — indicators, dimensions, dimension values, and data queries
- Configurable base URL and service-operation deadline (`GHO_BASE_URL`, `GHO_REQUEST_TIMEOUT_MS`) for custom or mirrored deployments
- Parallel metadata fan-out for multi-code indicator lookups
- Deterministic, total row/value ordering — pagination never repeats or drops rows across pages
Agent-friendly output:
- Tool descriptions encode the cross-tool workflow — agents discover the right call order (search → metadata → query) from descriptions alone
- Structured pagination signaling (`hasMore`, `nextOffset`, `pageInfo`, and `truncated` on the data-query tool) so agents can decide whether to page further
- Discriminated, typed error reasons with a `recovery` hint on every failure path
- Distinct empty-page vs. not-found semantics — paging past the end, an unmatched filter, and a genuinely missing code each report differently instead of colliding into one generic empty result
## Getting started
### Public Hosted Instance
A public instance is available at `https://who-gho.caseyjhand.com/mcp` — no installation required. Point any MCP client at it via Streamable HTTP:
```json
{
"mcpServers": {
"who-gho-mcp-server": {
"type": "streamable-http",
"url": "https://who-gho.caseyjhand.com/mcp"
}
}
}
```
### Self-Hosted / Local
Add the following to your MCP client configuration file.
```json
{
"mcpServers": {
"who-gho-mcp-server": {
"type": "stdio",
"command": "bunx",
"args": ["@cyanheads/who-gho-mcp-server@latest"],
"env": {
"MCP_TRANSPORT_TYPE": "stdio",
"MCP_LOG_LEVEL": "info"
}
}
}
}
```
Or with npx (no Bun required):
```json
{
"mcpServers": {
"who-gho-mcp-server": {
"type": "stdio",
"command": "npx",
"args": ["-y", "@cyanheads/who-gho-mcp-server@latest"],
"env": {
"MCP_TRANSPORT_TYPE": "stdio",
"MCP_LOG_LEVEL": "info"
}
}
}
}
```
Or with Docker:
```json
{
"mcpServers": {
"who-gho-mcp-server": {
"type": "stdio",
"command": "docker",
"args": ["run", "-i", "--rm", "-e", "MCP_TRANSPORT_TYPE=stdio", "ghcr.io/cyanheads/who-gho-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 ≥24).
- No API key required — the WHO GHO API is public.
### Installation
1. **Clone the repository:**
```sh
git clone https://github.com/cyanheads/who-gho-mcp-server.git
```
2. **Navigate into the directory:**
```sh
cd who-gho-mcp-server
```
3. **Install dependencies:**
```sh
bun install
```
4. **Configure environment:**
```sh
cp .env.example .env
# edit .env and set optional overrides
```
## Configuration
| Variable | Description | Default |
|:---|:---|:---|
| `MCP_TRANSPORT_TYPE` | Transport: `stdio` or `http` | `stdio` |
| `MCP_HTTP_PORT` | HTTP server port | `3010` |
| `MCP_HTTP_ENDPOINT_PATH` | HTTP endpoint path where the MCP server is mounted | `/mcp` |
| `MCP_SESSION_MODE` | HTTP session posture: `stateless`, `stateful`, or `auto`. No tool asks the caller for input mid-handler, so the server declares `stateless`; set this only to override. | `stateless` |
| `MCP_PUBLIC_URL` | Public origin override for TLS-terminating reverse-proxy deployments | none |
| `MCP_AUTH_MODE` | Authentication: `none`, `jwt`, or `oauth` | `none` |
| `MCP_LOG_LEVEL` | Log level (`debug`, `info`, `warning`, `error`, etc.) | `info` |
| `MCP_GC_PRESSURE_INTERVAL_MS` | Opt-in Bun-only forced-GC pressure loop (ms). Try `60000` if RSS grows under sustained HTTP load. | `0` (disabled) |
| `LOGS_DIR` | Directory for log files (Node.js only) | `/logs` |
| `STORAGE_PROVIDER_TYPE` | Storage backend: `in-memory`, `filesystem`, `supabase`, `cloudflare-kv/r2/d1` | `in-memory` |
| `GHO_BASE_URL` | WHO GHO OData API base URL (override for custom/mirrored deployments) | `https://ghoapi.azureedge.net/api/` |
| `GHO_REQUEST_TIMEOUT_MS` | Service-operation deadline in milliseconds, covering requests, body reads, retries, and backoff | `30000` |
| `GHO_CLAMP_LIMITS` | Clamp positive integer page limits to 100 for search, 500 for indicator/dimension browsing, and 1,000 for data queries, with a notice. Metadata processes 10 entries and returns continuation. `false` restores advertised maxima and rejection of oversized requests. | `true` |
| `OTEL_ENABLED` | Enable OpenTelemetry | `false` |
| `OTEL_EXPORTER_OTLP_ENDPOINT` | OTLP base URL; traces and metrics export to `/v1/traces` and `/v1/metrics` under it. Log export is opt-in through `OTEL_EXPORTER_OTLP_LOGS_ENDPOINT`. | none |
| `LOG_TOOL_FAILURE_PAYLOADS` | Log each failed tool call's arguments and result (key-name redaction only) | `false` |
See [`.env.example`](./.env.example) for the full list of optional overrides.
## Running the server
### Local development
- **Build and run the production version**:
```sh
# One-time build
bun run rebuild
# Run the built server
bun run start:http
# or
bun run start:stdio
```
- **Run checks and tests**:
```sh
bun run devcheck # Lints, formats, type-checks, and more
bun run test # Runs the test suite
```
### Docker
```sh
docker build -t who-gho-mcp-server .
docker run --rm -p 3010:3010 who-gho-mcp-server
```
The Dockerfile defaults to HTTP transport, stateless session mode, and logs to `/var/log/who-gho-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 the GHO service. |
| `src/config` | Server-specific environment variable parsing and validation with Zod. |
| `src/mcp-server/tools` | Tool definitions (`*.tool.ts`). Six tools across indicator discovery, dimension lookup, and data queries. |
| `src/mcp-server/resources` | Resource definitions. Indicator metadata and dimension values resources. |
| `src/services/gho` | WHO GHO OData API service layer — HTTP client, query builder, types. |
| `src/utils` | `wellFormed()` — repairs unpaired UTF-16 surrogates in caller-supplied strings before they reach output, enrichment, or failure data. |
| `tests/` | Unit and integration tests, mirroring the `src/` structure. |
## 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 logging, `ctx.state` for storage
- Register new tools and resources in the `createApp()` arrays
- Wrap external API calls: 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.