Overview

Measured air quality from the OpenAQ v3 API: physical-sensor observations from government reference monitors and research-grade sensors worldwide. Find monitoring stations, read current values, and pull historical pollutant series from any MCP client. Runs as a stdio process, a local Streamable HTTP server, or the public hosted endpoint above.

Tools

Resources

Both resources mirror tool output, so tool-only clients lose nothing.

Capability reference

openaq_find_locations _tool

• Scope by coordinates with radius (metres, 1–25000, default 12000), bbox, and/or iso (a code from openaq_list_countries); at least one is required, and coordinates and bbox exclude each other. parametersId, monitor, mobile, and providersId narrow further; up to 100 stations per page (limit, default 20), 1-based page
• Each station carries id, distanceMeters (coordinate search only), provider/providerId, isMonitor/isMobile, its parameters with units, and the datetimeFirst/datetimeLast span; coordinates, country, and provider are null when OpenAQ lists none
• totalCount counts stations through the current page and is a floor when totalCountIsLowerBound is set; no match fails as no_locations_found, a page past the end as page_exhausted

openaq_get_readings _tool

• A locationId, or coordinates plus parametersId to resolve the nearest station within 25 km that measures it (compared across up to 1,000 matching stations; a full 1,000 adds a notice); with locationId, parametersId optionally filters to one parameter
• One reading per sensor with value, unit, sensorId, and datetimeUtc/datetimeLocal, plus the station's provider, providerId, timezone, and datetimeLast
• Misses are typed: location_not_found, parameter_not_at_location (with the station's available ids), no_station_near_coordinates, no_recent_values

openaq_get_measurements _tool

• Requires locationId and parametersId; datetimeFrom/datetimeTo accept UTC timestamps or station-local YYYY-MM-DD dates (UTC days when the station has no timezone). aggregation is raw (default), hourly, or daily; up to 5,000 rows per call
• Returns series, sensorId, pulledCount, pullComplete, effectiveRange, and station provider, providerId, and timezone. totalCount is a floor when totalCountIsLowerBound is set; rollups add summary statistics, gapCount, the first 20 missing intervals as gaps, and a notice when edge buckets are clipped
• Past 100 rows, series is a preview (truncated) and the pulled rows stage on a DataCanvas as measurements_<sensorId> (canvasId, tableName) when CANVAS_PROVIDER_TYPE=duckdb; a supplied canvas_id stages onto that canvas at any size. One table per sensor: a second sensor adds a table to join against, and re-staging the same sensor overwrites its earlier series

openaq_list_parameters _tool

• Optional case-insensitive query over code, display name, and description; pollutantsOnly drops meteorological and particle-count channels
• Rows carry id, name, displayName, unit, and description; one pollutant can appear under several ids by unit (CO is 4 in µg/m³, 8 in ppm, 102 in ppb)

openaq_list_countries _tool

• Optional query (a two-letter value matches an ISO 3166-1 alpha-2 code first; otherwise code or name substrings match) and parametersId; up to 100 per page (limit, default 20), 1-based page
• Rows carry code (the iso value for openaq_find_locations), name, the datetimeFirst/datetimeLast span, and the parameters measured anywhere in the country; totalCount is the full filtered count

openaq_dataframe_describe _tool

• Takes a canvas_id from openaq_get_measurements and returns each staged table's name, rowCount, and columns. Call it before openaq_dataframe_query: the staged table is flat (min, sd) while the inline series nests those under summary
• Fails as canvas_unavailable unless CANVAS_PROVIDER_TYPE=duckdb, or canvas_not_found for an unknown or expired id

openaq_dataframe_query _tool

• A canvas_id and one read-only SELECT; writes, DDL, and file/network table functions are rejected
• At most 200 rows per response, with truncated set when the cap cut the result; page with ORDER BY plus LIMIT/OFFSET
• Fails as canvas_unavailable, canvas_not_found, or missing_table

openaq_dataframe_drop _tool

• Registered only with OPENAQ_ENABLE_CANVAS_DROP=true; calls fail as canvas_unavailable unless CANVAS_PROVIDER_TYPE=duckdb. When disabled, the HTTP landing page shows the enable hint and tools/list omits the tool
• Takes a canvas_id and deletes that whole canvas, including all staged tables. Other agents sharing the id lose access; OpenAQ's source data is unaffected
• Returns the requested canvasId and dropped: true when deleted, false when no reachable canvas exists. With authentication off, callers share a tenant: anyone holding an id can delete its canvas when enabled

openaq://location/{locationId} _resource

• application/json: name, locality, timezone, country, provider, isMonitor/isMobile, coordinates, sensors (each with parameterId and unit), and the datetimeFirst/datetimeLast span
• locationId comes from openaq_find_locations; cached 5 minutes

openaq://parameters _resource

• application/json catalog, the same rows as an unfiltered openaq_list_parameters
• Cached 1 hour

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.

OpenAQ-specific:

• One typed client over the OpenAQ v3 REST API: X-API-Key auth, retry with backoff, and typed upstream failures (invalid_api_key, rate_limited, upstream_timeout, upstream_error) on every OpenAQ call
• Hides the v3 location → sensor → measurement hierarchy: readings join the latest feed to the station's sensor map, and measurements resolve a station plus parameter to its sensor
• Coordinates and bbox corners are range-checked and contradictory search scopes rejected before any request reaches OpenAQ
• Large measurement series stage on a DataCanvas for read-only DuckDB SQL, one table per sensor, so two series on one canvas_id can be joined

Agent-friendly output:

• Measured, not modeled: a search with no station fails as no_locations_found or no_station_near_coordinates, stated as no coverage rather than clean air
• Units travel with every value and are never converted; parametersId selects pollutant and unit together
• Freshness and truncation are explicit: per-value timestamps and datetimeLast, and totalCount / truncated / notice on capped results

Getting started

Public Hosted Instance

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

{
  "mcpServers": {
    "openaq-mcp-server": {
      "type": "streamable-http",
      "url": "https://openaq.caseyjhand.com/mcp"
    }
  }
}

Self-Hosted / Local

Add the following to your MCP client configuration file.

{
  "mcpServers": {
    "openaq-mcp-server": {
      "type": "stdio",
      "command": "bunx",
      "args": ["@cyanheads/openaq-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "OPENAQ_API_KEY": "your-api-key"
      }
    }
  }
}

Or with npx (no Bun required):

{
  "mcpServers": {
    "openaq-mcp-server": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@cyanheads/openaq-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "OPENAQ_API_KEY": "your-api-key"
      }
    }
  }
}

Or with Docker:

{
  "mcpServers": {
    "openaq-mcp-server": {
      "type": "stdio",
      "command": "docker",
      "args": [
        "run", "-i", "--rm",
        "-e", "MCP_TRANSPORT_TYPE=stdio",
        "-e", "OPENAQ_API_KEY=your-api-key",
        "ghcr.io/cyanheads/openaq-mcp-server:latest"
      ]
    }
  }
}

Add "CANVAS_PROVIDER_TYPE": "duckdb" to env to enable DataCanvas SQL over large measurement series.

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

MCP_TRANSPORT_TYPE=http MCP_HTTP_PORT=3010 OPENAQ_API_KEY=your-api-key bun run start:http
# Server listens at http://localhost:3010/mcp

Prerequisites

• Bun v1.4.0 or higher (or Node.js v24+).
• A free OpenAQ v3 API key from an OpenAQ Explorer account.

Installation

1. Clone the repository:

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

2. Navigate into the directory:

cd openaq-mcp-server

3. Install dependencies:

bun install

4. Configure environment:

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

Configuration

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

Running the server

Local development

• Build and run:

  shCopy

  bun run rebuild
  bun run start:http   # or start:stdio
  

• Run checks and tests:

  shCopy

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

Docker

docker build -t openaq-mcp-server .
docker run --rm -e OPENAQ_API_KEY=your-api-key -p 3010:3010 openaq-mcp-server

The image defaults to HTTP transport, stateless session mode, and logs to /var/log/openaq-mcp-server. DuckDB ships in the image, so DataCanvas works once CANVAS_PROVIDER_TYPE=duckdb is set. OpenTelemetry peer dependencies are installed by default; build with --build-arg OTEL_ENABLED=false to omit them.

Project structure

Development guide

See CLAUDE.md / AGENTS.md for development guidelines and architectural rules. The short version:

• Handlers throw, framework catches — catch only to map a failure to a declared error reason or to keep a partial result
• Use ctx.log for request-scoped logging, ctx.state for tenant-scoped storage
• Register new tools and resources in the createApp() arrays
• Wrap the OpenAQ API: validate raw → normalize to the domain type → return the output schema; surface units verbatim and 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.

Data comes from the OpenAQ platform, and attribution to OpenAQ is required when using this server's output (Terms of Use). OpenAQ aggregates measurements from government agencies, research institutions, and other networks, each of which may set its own attribution or licensing terms. The provider field on openaq_find_locations, openaq_get_readings, and openaq_get_measurements results and the openaq://location/{locationId} resource names the originating network; review and follow the terms of any provider whose data you use.