@cyanheads/nominatim-mcp-server

@cyanheads/nominatim-mcp-server

Geocode, reverse geocode, and run Overpass spatial queries on OpenStreetMap data via MCP. STDIO or Streamable HTTP.

6 Tools

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

Tools

6 tools for geocoding and spatial queries against OpenStreetMap data:

Tool	Description
nominatim_geocode	Convert a place name or address to geographic coordinates and structured place data
nominatim_reverse	Convert latitude/longitude coordinates to the nearest address or place name
nominatim_lookup	Fetch address details for one or more known OSM objects by their IDs
overpass_query_nearby	Find OSM features within a radius around a geographic point
overpass_query_bbox	Find OSM features within a rectangular bounding box
overpass_query_raw	Execute a raw Overpass QL query for advanced spatial operations

nominatim_geocode

Convert a place name or address to geographic coordinates via Nominatim/OpenStreetMap.

• Two input modes: free-form query string (e.g., "Space Needle Seattle") or structured address fields (street, city, state, country, postal code) — mutually exclusive
• Country filtering via ISO 3166-1 alpha-2 codes (countrycodes)
• Data layer filtering: address, poi, railway, natural, manmade
• Feature type restriction: country, state, city, settlement
• Optional extra OSM tags (phone, website, opening_hours, wikidata)
• Preferred language override via BCP 47 code
• Returns results ordered by Nominatim importance score (global prominence)
• Results include coordinates, structured address, bounding box, OSM type/ID for chaining into nominatim_lookup

nominatim_reverse

Convert latitude/longitude to the nearest address or named place.

• Zoom-level control for address detail: 18=building, 16=street, 14=neighbourhood, 12=town, 10=city, 8=county, 5=state, 3=country
• Layer filtering for matched OSM object type
• Optional extra OSM tags and language preference
• Returns structured address breakdown, OSM type/ID, and bounding box

nominatim_lookup

Fetch full Nominatim address records for known OSM object IDs.

• Accepts single ID or array of up to 50 IDs
• IDs must be prefixed with N (node), W (way), or R (relation): e.g., "N240109189", "W50637691", "R146656"
• Efficient alternative to a full geocoding round-trip when OSM IDs are already known (e.g., from an Overpass result)
• Reports not_found list for IDs that returned no result
• Optional extra OSM tags and language preference

overpass_query_nearby

Find OSM features within a radius around a point via the Overpass API.

• Primary tool for "what's near X?" spatial queries
• Supports amenity shortcut for common POI types (hospital, pharmacy, restaurant, cafe, school, atm) or tag_key + tag_value for any OSM category (leisure=park, shop=supermarket, natural=peak)
• Configurable radius up to 50km; keep under 5km for dense urban POI queries
• Element type filtering: node (standalone POIs), way (buildings/areas), relation (complex structures)
• Limit up to 500 results; truncated flag signals when more exist
• Returns OSM type/ID, coordinates, name, and full tag set for each feature

overpass_query_bbox

Find OSM features within a rectangular geographic bounding box.

• Useful for area surveys where proximity to a single point isn't the goal
• Same amenity / tag_key + tag_value interface as overpass_query_nearby
• Configurable timeout for large bounding boxes or dense areas
• Limit up to 500 results with truncated flag

overpass_query_raw

Execute arbitrary Overpass QL for queries the convenience tools don't cover.

• Full Overpass QL expressiveness: multi-type queries, union queries, relation membership, historical queries
• Query must include [out:json]; server injects [timeout:N] if absent
• Returns raw element array — structure varies by query type (nodes have lat/lon, ways have nodes[], relations have members[])
• Validate complex queries at overpass-turbo.eu before use

Features

Built on @cyanheads/mcp-ts-core:

• Declarative tool definitions — single file per tool, framework handles registration and validation
• Unified error handling across all tools
• Pluggable auth (none, jwt, oauth)
• Swappable storage backends: in-memory, filesystem, Supabase, Cloudflare KV/R2/D1
• Structured logging with optional OpenTelemetry tracing
• Runs locally (stdio/HTTP) or on Cloudflare Workers from the same codebase

Nominatim/Overpass-specific:

• Nominatim usage policy compliance: configurable User-Agent via NOMINATIM_USER_AGENT, rate-limit-aware request handling
• OSM attribution on every response (Data © OpenStreetMap contributors, ODbL 1.0)
• Private instance support — override NOMINATIM_BASE_URL and OVERPASS_BASE_URL for self-hosted or mirror endpoints
• Structured error contracts: no_results, no_coverage, invalid_id_format, invalid_tag, query_timeout, rate_limited, query_error, result_too_large — all with actionable recovery hints

Agent-friendly output:

• Attribution on every response — agents can surface the ODbL license notice as required
• Structured output contracts — coordinates, OSM IDs, address fields, and tag maps in consistent shapes
• Cross-tool chaining: Overpass results carry osm_type + osm_id that feed directly into nominatim_lookup for full address records

Getting started

Self-Hosted / Local

Add the following to your MCP client configuration file.

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

Or with npx (no Bun required):

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

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 v1.3.0 or higher (or Node.js ≥24.0.0).
• No API key required — Nominatim and Overpass are public APIs. For heavy use, consider pointing NOMINATIM_BASE_URL and OVERPASS_BASE_URL at self-hosted or mirror instances.

Installation

• Clone the repository:

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

• Navigate into the directory:

cd nominatim-mcp-server

• Install dependencies:

bun install

Configuration

All configuration is validated at startup via Zod schemas in src/config/server-config.ts. Key environment variables:

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_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). Recommended starting point if heap growth is observed: 60000.	0 (disabled)
STORAGE_PROVIDER_TYPE	Storage backend: in-memory, filesystem, supabase, cloudflare-kv/r2/d1	in-memory
NOMINATIM_BASE_URL	Nominatim API base URL. Override for a private or mirror instance.	https://nominatim.openstreetmap.org
OVERPASS_BASE_URL	Overpass API endpoint URL. Override for a mirror or private instance.	https://overpass-api.de/api/interpreter
NOMINATIM_USER_AGENT	User-Agent sent to Nominatim and Overpass. Required by usage policy.	nominatim-mcp-server/0.1.8
OTEL_ENABLED	Enable OpenTelemetry	false

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/mcp-server/tools	Tool definitions (*.tool.ts). Six tools across Nominatim and Overpass.
src/services/nominatim	Nominatim service layer — API client, search, reverse, lookup.
src/services/overpass	Overpass service layer — query builder, executor, element normalizer.
src/config	Server-specific environment variable parsing and validation with Zod.

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

Contributing

Issues and pull requests 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.

Map data from OpenStreetMap contributors, available under the Open Database License (ODbL).