@cyanheads/geonames-mcp-server

Public Hosted Server: https://geonames.caseyjhand.com/mcp

Overview

The GeoNames gazetteer: 13M+ places worldwide, linked into an administrative tree from continent to neighborhood. Search places, read full records, walk the admin hierarchy, reverse geocode coordinates, look up postal codes, and read country facts.

Tools

Related MCP server: GeoWire

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, by ISO alpha-2, alpha-3, or numeric code), adminCode1–adminCode4, featureClasses, featureCodes (up to 20), cities (cities1000 / cities5000 / cities15000), and boundingBox. A call needs query or one of countries, featureClasses, featureCodes, boundingBox

• A listed country also returns the territories GeoNames files under it (GB also returns IM, GG, JE, and GS), each place under its own countryCode; the notice names any country on the page that countries does not list

• adminCode1–adminCode4 search inside an admin division by its GeoNames code, as geonames_get_place and geonames_reverse_geocode return it in adminLevels (countries: ["US"], adminCode1: "TX", featureCodes: ["AIRP"] lists Texas airports). Codes are case-insensitive and zero padding counts (02, not 2); they are not ISO 3166-2 or postal codes (Bavaria is 02, not BY). Each needs exactly one country, and levels 2–4 need adminCode1

• limit 1–1,000 (default 10), held to 100 per call with a notice when more remain; offset 0–5000, orderBy relevance or population (omitted, GeoNames' own order); returns totalCount, effectiveQuery, and nextOffset

• featureClasses, featureCodes, and cities (class P only) intersect: with both lists set, each code's class must be listed and each listed class needs a code; beside cities, only class P and its codes. Anything else fails as feature_filter_mismatch

• Fails before any request with query_or_filter_required, query_required, unknown_country_code, unknown_feature_code, admin_code_unscoped, feature_filter_mismatch, or invalid_bounding_box

geonames_get_place tool

• One geonameId; an unknown id returns found: false with guidance

• Returns adminLevels 1–5 (code, name, 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)

• The timezone is the zone GeoNames associates with the record. On a record with no country (an ocean, a sea, a continent) a notice says so and gives the geonames_reverse_geocode call for the time at its coordinates

• postalCodes lists the codes GeoNames links to the feature, which can be fewer than geonames_find_postal_codes returns for the place

• nameLanguages (up to 20 tags; zh also matches zh-CN) filters alternateNames 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 (islands, coasts, and their municipalities; almost all in Spain), or dependency (a country's dependent territories). Children are mostly admin divisions (class A) and populated places (class P); continents and coasts are class L, islands class T

• GeoNames answers a tourism or dependency request with the administrative children when the feature has no such tree. The tool compares the two lists and sets sameAsAdministrative, with a notice, when they match; the rows stay, since a real tree can match too

• Fetches up to 1,000 children per parent once and caches them, so nameContains, limit (1–1,000, default 100, held to 500 per call with a notice when more remain), and offset cost no extra credits; a notice says when GeoNames lists more. A nameContains with no letter or digit fails before any request as name_contains_unsearchable

• 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

• coastalBufferKm (0–50, default 0) matches the nearest country within that distance when none contains the point, for harbor, pier, and shoreline fixes; a buffered match carries country.distanceInKm, and the nearby and timezone lookups keep the exact point

• nearby lists the nearest populated places (nearbyLimit 0–1,000, default 5, held to 50 per call with a notice when more lie within the radius; radiusKm up to 300, default 20; optional cities tier) or, when featureClasses / featureCodes is set, the nearest features of that type; nearbyKind says which. featureClasses and featureCodes intersect

• When more than 50 lie within the radius, the notice prints the geonames_search_places call, with a boundingBox enclosing the radius, that lists them, up to the search's 5,100-row reach. The search returns rows by relevance, not distance, so read every page and keep the rows within radiusKm

• Fails before any request with conflicting_filters (cities with a feature filter), unknown_feature_code, or feature_filter_mismatch (a code whose class is not listed, or a listed class with no code)

• includeTimezone adds the IANA id, UTC offsets, local time, sunrise, and sunset (offsets only offshore, where both dates are reported at the standard offset)

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 or an offset above 0 in nearby, fails as mode_fields_mismatch

• countries filter for code and place_name, by ISO alpha-2, alpha-3, or numeric code (the 250 country codes plus the retired AN, CS, and YU; any other, such as EL or ZZZ, fails as unknown_country_code)

• A listed country also returns the territories GeoNames files under it (GB also returns IM, JE, and GG), each postal code under its own countryCode; the notice names any country on the page that countries does not list

• limit 1–1,000 (default 10), held to 100 per call with a notice when more remain; code and place_name page with offset 0–5000 and return nextOffset while more rows remain below offset 5000; GeoNames reports no total, so truncated says whether more rows exist, never how many

• Covers 122 countries; Ireland returns only Eircode routing keys and Malta only letter prefixes

• Admin codes on postal rows come from the postal dataset and can differ from the gazetteer's (Bavaria is BY here, 02 in search), so they are not geonames_search_places filters

geonames_get_countries tool

• Up to 250 countries by ISO alpha-2, alpha-3, or numeric code, a continent, nameContains, or no filter for all 250; limit 1–1,000 (default 50), held to 250 per call, with offset; a nameContains with no letter or digit fails before any request as name_contains_unsearchable

• Rows carry ISO and FIPS codes, 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 1–1,000 (default 100, held to 700 per call, which fits every topic), and offset; feature classes and codes are bundled and spend no credits. A nameContains with no letter or digit fails before any request as name_contains_unsearchable

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.

• Per-account pacing at 1,000 requests an hour, with a cooldown after a quota error that holds only that account

• Responses are cached across callers: searches for 1 hour, timezones never, every other lookup for 24 hours. A cache hit spends no credit

• Forgiving inputs: alpha-3 and numeric country codes, UK for GB, and FL for LI. The server also accepts forms its advertised schemas leave out (a comma-joined string for a list, other casings of enums and codes, a P.PPLC class prefix, a geonames.org URL or a JSON integer for a geonameId, extra spaces in a postal code, username for geonamesUsername), but the tool descriptions offer only the canonical forms, since a client that validates arguments refuses the rest

Agent-friendly output:

• Typed failure reasons 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; empty or partial pages carry a notice naming the next offset or the filter to loosen

• GeoNames placeholders for "none" (population: 0, empty admin names, geonameId: 0) are dropped rather than reported as facts

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 window resets.

• Search and postal searches reach only offset 5000 on the free tier, and a page holds at most 100 rows, so a result set is reachable up to its 5,100th row. Nearby postal lookups do not page: they return the nearest 100, which in a dense city covers little ground (0.19 km in central London).

• Children cap at 1,000 per parent.

• 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.

• Nearby radius tops out at 300 km for places and features and 30 km for postal codes, GeoNames' free-tier ceilings.

• Bounding boxes cannot cross the 180° meridian. Split such an area into two searches.

• Coastal points can resolve to the ocean without a buffer. By default only a country that contains the point matches, so a harbor or shoreline point just outside the outline returns the sea while its nearby places are on land. Set coastalBufferKm (up to 50) to match the nearest country instead; in a strait that can be either shore.

• Microstates and enclaves can resolve to the surrounding country. 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. cities restricts to places above a population tier, but a city section (PPLX) with its own population passes it.

• Offshore timezones are offsets only. No IANA id, local time, sunrise, or sunset is available at sea, and both dated offsets are the standard offset (open water has no DST).

• A place record's timezone is GeoNames' association, not a lookup at its coordinates. On a record with no country it can be far off (South Pacific Ocean carries Pacific/Tongatapu, +13), and a country-bearing record can still carry another country's zone, as some Antarctic seas do. geonames_reverse_geocode with includeTimezone gives the time at a point.

• 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 or elevation.

Getting started

Connect to the hosted instance, no install:

claude mcp add --transport http geonames-mcp-server https://geonames.caseyjhand.com/mcp

A call that passes no geonamesUsername spends the hosted instance's GeoNames account, whose 1,000 credits an hour are shared by every such caller. Pass your own geonamesUsername to spend your account's quota instead.

Or run it locally:

claude mcp add geonames-mcp-server -e GEONAMES_USERNAME=your_geonames_username -- npx -y @cyanheads/geonames-mcp-server

For other clients, add this to the MCP config file:

{
  "mcpServers": {
    "geonames-mcp-server": {
      "command": "npx",
      "args": ["-y", "@cyanheads/geonames-mcp-server"],
      "env": { "GEONAMES_USERNAME": "your_geonames_username" }
    }
  }
}

Create a free GeoNames account, then enable free web services on its account page; GeoNames rejects calls from an account until they are enabled. For Docker or a source build, see Running the server.

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, 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.

A free account gets 1,000 credits an hour and 10,000 a day. Cached lookups spend nothing.

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

Running the server

Local development

Requires Bun v1.4.0 or higher (or Node.js v24+).

• Clone and install:

  git clone https://github.com/cyanheads/geonames-mcp-server.git
  cd geonames-mcp-server && bun install
  cp .env.example .env   # set GEONAMES_USERNAME

• Build and run:

  # One-time build
  bun run rebuild
  
  # Run the built server
  bun run start:stdio
  # or
  bun run start:http   # listens at http://localhost:3010/mcp

• Run checks and tests:

  bun run devcheck   # Lint, format, typecheck, security
  bun run test       # Vitest test suite
  bun run lint:mcp   # Validate MCP definitions against spec

Docker

docker run --rm -e GEONAMES_USERNAME=your_geonames_username -p 3010:3010 ghcr.io/cyanheads/geonames-mcp-server:latest

The image defaults to HTTP transport, stateless session mode, and logs to /var/log/geonames-mcp-server. To run it over stdio from an MCP client, use "command": "docker" with "args": ["run", "-i", "--rm", "-e", "MCP_TRANSPORT_TYPE=stdio", "-e", "GEONAMES_USERNAME=your_geonames_username", "ghcr.io/cyanheads/geonames-mcp-server:latest"]. To build locally, docker build -t geonames-mcp-server .; OpenTelemetry peer dependencies are installed by default — build with --build-arg OTEL_ENABLED=false to omit them.

Project 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 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.