who-gho-mcp-server

---

Overview

WHO Global Health Observatory (GHO) data — 3,059 indicators across 194 member states. Search the indicator catalog, discover country, region, income-group, and sex filter dimensions, and query data rows from any MCP client. Runs as a stdio process, a local Streamable HTTP server, or the public hosted endpoint above.

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 supported filter dimensions for up to 10 codes
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.

Capability reference

who_search_indicators _tool

• Substring match on indicator names — try terms like "life expectancy", "immunization", "mortality", "diabetes", or "HIV"
• 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 — lists all 3,059+ catalog indicators
• Offset-based pagination via limit (default 50, max 500) and offset
• Returns totalCount and hasMore for iteration

---

who_get_indicator_metadata _tool

• Accepts 1–10 indicator codes per call, fetched in parallel
• Returns the full indicator name and supported dimension types (e.g. COUNTRY, SEX, REGION, AGEGROUP) for each resolved code
• Roughly 1,300 catalog indicators have no dimension listing upstream — those return dimensions: [] plus a dimensionsNote pointing at a sample data row's dim1Type/dim2Type, not a not-found
• Codes absent from the catalog land in notFound rather than raising an error; the call fails only when none of the requested codes resolve

---

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, not an error; only an unfiltered empty result means the dimension itself does not exist
• 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 (ISO 3166-1 alpha-3), region_codes (WHO regions), or income_group_codes (World Bank groups) — 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, otherwise use dim1_value
• 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, not an error — read the unfiltered URI to confirm the dimension itself exists
• Same output shape as the bare and paged resources: dimension, values, totalCount, hasMore, nextOffset, notice

Features

Built on @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 — indicators, dimensions, dimension values, and data queries
• Configurable base URL and request timeout (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:

{
  "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.

{
  "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):

{
  "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:

{
  "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:

MCP_TRANSPORT_TYPE=http MCP_HTTP_PORT=3010 bun run start:http
# Server listens at http://localhost:3010/mcp

Prerequisites

• Bun v1.4.0 or higher (or Node.js ≥24).
• No API key required — the WHO GHO API is public.

Installation

1. Clone the repository:

git clone https://github.com/cyanheads/who-gho-mcp-server.git

2. Navigate into the directory:

cd who-gho-mcp-server

3. Install dependencies:

bun install

4. Configure environment:

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)	<project-root>/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	HTTP request timeout in milliseconds	30000
OTEL_ENABLED	Enable OpenTelemetry	false

See .env.example for the full list of optional overrides.

Running the server

Local development

• Build and run the production version:

  # One-time build
  bun run rebuild
  
  # Run the built server
  bun run start:http
  # or
  bun run start:stdio
  

• Run checks and tests:

  bun run devcheck  # Lints, formats, type-checks, and more
  bun run test      # Runs the test suite
  

Docker

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 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:

bun run devcheck
bun run test

License

Apache-2.0 — see LICENSE for details.