geonames-mcp-server

---

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

Tool	Description
geonames_search_places	Search places by name, country, admin division code, 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, 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, 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)
• 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
• 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
• 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

---

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
• 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

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.
• 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, 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, and both dated offsets are the standard offset (open water has no DST).
• 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

Public Hosted Instance

A public instance is available at https://geonames.caseyjhand.com/mcp — no installation required. Point any MCP client at it via Streamable HTTP:

{
  "mcpServers": {
    "geonames-mcp-server": {
      "type": "streamable-http",
      "url": "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.

Self-Hosted / Local

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, 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.

Tool	Credits per call
geonames_search_places, geonames_get_place, geonames_get_hierarchy	1
geonames_get_children	1; 2 for tourism or dependency when the parent's administrative list is not cached
geonames_find_postal_codes	1 (code, place_name; a miss with countries adds 1 for the postal coverage list unless it is cached); 2 (nearby)
geonames_reverse_geocode	1 for containment (with or without coastalBufferKm), plus 3 for nearest populated places or 4 for nearest features, 1 for the ocean when no country contains the point or lies within the buffer, 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: a GeoNames username is removed under geonamesUsername, username, or any near-miss key with a user or account word.	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 and country-code tables.
src/utils	Inline-text sanitizer for GeoNames-authored and caller-echoed text in format() output and the enrichment trailer renders.
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.