geonames-mcp-server

---

Overview

The GeoNames gazetteer: 13M+ places worldwide, each keyed by a stable integer geonameId and linked into an administrative tree from continent to neighborhood. Search places by name and filters, read a place's full record, climb or descend its admin hierarchy, reverse geocode a coordinate, look up postal codes, and read country facts. Runs as a stdio process or a local Streamable HTTP server.

Tools

Tool	Description
geonames_search_places	Search places by name, country, feature class or code, population tier, and bounding box
geonames_get_place	Full record for one geonameId: admin chain, timezone, elevation, alternate names, postal codes, external identifiers
geonames_get_hierarchy	Parent chain from Earth and the continent down to the feature
geonames_get_children	Direct children of a feature in the administrative, tourism, geography, or dependency tree
geonames_reverse_geocode	Country and admin subdivisions (or the ocean) for a coordinate, plus the nearest places or features and an optional timezone
geonames_find_postal_codes	Postal codes by code, by place name, or near a coordinate
geonames_get_countries	Country facts: ISO and FIPS codes, geonameId, capital, population, area, languages, currency, postal-code format
geonames_list_reference	Feature classes, feature codes, and the countries with postal-code data

Capability reference

geonames_search_places _tool

• query (up to 200 characters) compared per match: name_required (default), any_field, exact_name, or name_prefix; filters countries (up to 10), featureClasses, featureCodes (up to 20), cities (cities1000 / cities5000 / cities15000), and boundingBox. A call needs query or at least one of countries, featureClasses, featureCodes, boundingBox
• limit 1–100 (default 10), offset 0–5000, orderBy relevance or population; reports totalCount and the effectiveQuery sent, and nextOffset names the next page
• Fails before any request with query_or_filter_required, query_required, unknown_feature_code, or invalid_bounding_box

---

geonames_get_place _tool

• One geonameId; an unknown id returns found: false with guidance
• adminLevels 1–5 with each level's code, name, and geonameId; timezone (UTC offsets on 1 January and 1 July), bounding box, recorded and DEM elevation, population, Wikipedia URL, alternateNames, postalCodes, links, and identifiers (IATA, ICAO, FAA, Transport Canada, UN/LOCODE, Wikidata)
• nameLanguages (up to 20 tags; zh also matches zh-CN and zh-TW) filters the alternate names only

---

geonames_get_hierarchy _tool

• One geonameId; chain runs from Earth and its continent through the country and admin divisions down to the feature, skipping levels it does not sit under
• Each level carries geonameId, feature class and code, country and first-level codes, coordinates, and population; an unknown id returns found: false

---

geonames_get_children _tool

• hierarchy: administrative (default), tourism, geography, or dependency; only admin divisions and populated places appear
• The child list (up to 1,000 per parent) is fetched once and cached, so nameContains, limit (1–500, default 100), and offset cost nothing more; a notice says when GeoNames lists more than 1,000
• An unknown id returns found: false; a leaf returns an empty children list with a notice

---

geonames_reverse_geocode _tool

• lat / lng resolve to country and adminLevels (down to ADM5, each with its geonameId and ISO 3166-2 subdivision code where one exists) or, offshore, the ocean
• nearby lists the nearest populated places (nearbyLimit 0–50, default 5; radiusKm up to 300, default 20; optional cities tier) or, when featureClasses / featureCodes is set, the nearest features of that type; nearbyKind says which. cities with a feature filter fails as conflicting_filters
• includeTimezone adds the IANA id, UTC offsets, local time, sunrise, and sunset (offsets only offshore)

---

geonames_find_postal_codes _tool

• mode: code (needs postalCode), place_name (needs placeName), or nearby (needs lat and lng; radiusKm up to 30, default 10); a missing field, or countries in nearby, fails as mode_fields_mismatch
• countries filter for code and place_name; limit 1–100 (default 10). GeoNames reports no total, so a full page is marked truncated
• Covers 122 countries; Ireland returns only Eircode routing keys and Malta only letter prefixes

---

geonames_get_countries _tool

• Up to 50 countries by ISO alpha-2, alpha-3, or numeric code, a continent, nameContains, or no filter for all 250; limit 1–250 (default 50) with offset
• Each row carries ISO and FIPS codes, the country's geonameId (the starting point for geonames_get_children), capital, population, area, continent, languages, currency, postal-code format, and mainland bounding box; unknown codes land in notFound

---

geonames_list_reference _tool

• topic: feature_classes (9), feature_codes (684, filterable by featureClass), or postal_countries (122, with each country's code range and count); featureClass with another topic fails as filter_not_applicable
• nameContains, limit 1–700 (default 100), and offset; feature classes and codes are bundled and spend no credits

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.

GeoNames-specific:

• Data from GeoNames, licensed CC BY 4.0: results you pass on must credit GeoNames. This server is independent of GeoNames.
• Calls the GeoNames JSON web services at secure.geonames.org through a fixed parameter allowlist per endpoint, since GeoNames silently ignores a parameter it does not know
• Per-account pacing at 1,000 requests an hour, with a cooldown after a GeoNames quota error that holds only that account
• A response cache shared across callers and keyed without the account: searches for 1 hour, timezones never, every other lookup for 24 hours. A cache hit spends no credit
• Forgiving inputs: comma-separated lists, any-case enums and codes, UK for GB, a P.PPLC class prefix, and a geonames.org URL in place of a geonameId

Agent-friendly output:

• Typed failure reasons that separate the caller's account (caller_account_rejected) from the operator's (server_account_rejected), a spent quota (quota_exhausted, with data.window of hour, day, week, or local), and a value GeoNames rejected (upstream_rejected_parameter)
• Unknown ids return found: false with guidance rather than an error, and empty or partial pages carry a notice naming the next offset or the filter to loosen
• Placeholders GeoNames uses for "none" (population: 0, empty admin names, geonameId: 0) are dropped rather than reported as facts
• GeoNames-authored text (place, alternate, and admin names) is rendered as inline data in content[] and kept verbatim in structuredContent

Known limitations:

• Shared quota on a shared deployment. All callers without their own username share the server account's 1,000 credits an hour. A burst of reverse geocodes (up to 7 credits each) can exhaust it, and GeoNames does not say when the hourly window resets.
• Search pages no further than offset 5000 on the free tier, and limit is capped at 100, so a result set is reachable up to its 5,100th row.
• Children are capped at 1,000 per parent. A notice says when GeoNames lists more than it returns.
• Postal data covers 122 countries. Ireland and Malta return only code prefixes. US nearby lookups place the first row at the query point rather than the ZIP centroid. GeoNames reports no total for postal searches, so truncation is inferred from a full page.
• Coastal points can resolve to the ocean. The subdivision lookup uses no coastal buffer, so a point just offshore returns the sea while its nearby places are on land.
• Bounding boxes cannot cross the 180° meridian. Split such an area into two searches.
• Nearby radius tops out at 300 km for places and features and 30 km for postal codes, GeoNames' free-tier ceilings.
• Microstates and enclaves can resolve to the surrounding country. The subdivision polygons do not always carve them out: a point inside Vatican City returns Italy.
• Nearest populated places include sections and historical places. In a dense city the nearest rows are often PPLX quarters or PPLH former districts; each row's featureCode says which, and cities restricts to places above a population tier.
• Offshore timezones are offsets only. No IANA id, local time, sunrise, or sunset is available at sea.
• exact_name matches alternate and historical names, so a result's name can differ from the query: "Springfield" can return Plattsburg or Palmyra, MO.
• Data is community-edited and provided "as is". Many features have no recorded population (reported as unavailable) or elevation.

Getting started

Add the following to your MCP client configuration file, with your GeoNames username in place of the placeholder.

{
  "mcpServers": {
    "geonames-mcp-server": {
      "type": "stdio",
      "command": "bunx",
      "args": ["@cyanheads/geonames-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info",
        "GEONAMES_USERNAME": "your_geonames_username"
      }
    }
  }
}

Or with npx (no Bun required):

{
  "mcpServers": {
    "geonames-mcp-server": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@cyanheads/geonames-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info",
        "GEONAMES_USERNAME": "your_geonames_username"
      }
    }
  }
}

Or with Docker:

{
  "mcpServers": {
    "geonames-mcp-server": {
      "type": "stdio",
      "command": "docker",
      "args": [
        "run", "-i", "--rm",
        "-e", "MCP_TRANSPORT_TYPE=stdio",
        "-e", "GEONAMES_USERNAME=your_geonames_username",
        "ghcr.io/cyanheads/geonames-mcp-server:latest"
      ]
    }
  }
}

For Streamable HTTP, set the transport and start the server:

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

Prerequisites

• Bun v1.4.0 or higher (or Node.js v24+).
• A free GeoNames account with free web services enabled on its account page. GeoNames rejects calls from an account until they are enabled.

Installation

1. Clone the repository:

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

2. Navigate into the directory:

cd geonames-mcp-server

3. Install dependencies:

bun install

4. Configure environment:

cp .env.example .env
# edit .env and set GEONAMES_USERNAME

Configuration

Every GeoNames call spends credits from a GeoNames account. GEONAMES_USERNAME is the server's account: a free GeoNames account with free web services enabled on its account page. Every tool also takes geonamesUsername (alias username), so a caller on a shared deployment can spend their own account instead of the server's. When neither is set, calls fail with username_required; only the bundled feature_classes and feature_codes topics of geonames_list_reference work without an account. The account name never appears in output, error text, logs, or cache keys.

A free account gets 1,000 credits an hour and 10,000 a day. Static lookups are cached, so a repeat call spends nothing.

Tool	Credits per call
geonames_search_places, geonames_get_place, geonames_get_hierarchy, geonames_get_children	1
geonames_find_postal_codes	1 (code, place_name); 2 (nearby)
geonames_reverse_geocode	1 for containment, plus 3 for nearest populated places or 4 for nearest features, 1 for the ocean when no country contains the point, and 1 for the timezone
geonames_get_countries	1 a day; the country table is cached
geonames_list_reference	0 for feature_classes and feature_codes; 1 a day for postal_countries

Variable	Description	Default
GEONAMES_USERNAME	GeoNames account used when a call passes no geonamesUsername. Free at geonames.org; enable free web services on its account page.	none
MCP_TRANSPORT_TYPE	Transport: stdio or http.	stdio
MCP_HTTP_PORT	HTTP server port.	3010
MCP_SESSION_MODE	HTTP session mode: stateless, stateful, or auto. .env.example and the Docker image set stateless.	auto
MCP_AUTH_MODE	Authentication: none, jwt, or oauth.	none
MCP_LOG_LEVEL	Log level (debug, info, warning, error, etc.).	info
LOGS_DIR	Directory for log files (Node.js only).	<app-root>/logs
LOG_TOOL_FAILURE_PAYLOADS	Log each failed tool call's arguments and result, redacted by key name (geonamesUsername and username included).	false
STORAGE_PROVIDER_TYPE	Storage backend: in-memory, filesystem, supabase, cloudflare-kv/r2/d1.	in-memory
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
  

Project structure

Directory	Purpose
src/index.ts	createApp() entry point: server instructions, tool registration, GeoNames service setup and teardown.
src/config	GEONAMES_USERNAME parsing and validation with Zod.
src/mcp-server/tools	The eight tool definitions (*.tool.ts) and the inputs they share (shared-inputs.ts).
src/services/geonames	GeoNames service: fetch boundary, status mapping, retry, per-account pacing, response cache, parsers, and the bundled feature-code table.
src/utils	Inline-text sanitizer for GeoNames-authored text in format() output.
tests/	Unit and integration tests, mirroring the src/ structure.
docs/design.md	Design notes: tool surface, credential model, upstream behavior.

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 in src/mcp-server/tools/definitions/index.ts
• 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

This project is licensed under the Apache 2.0 License. See the LICENSE file for details.