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mcp-server-jma

mcp-server-jma

by b84330808
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TypeScript
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mcp-server-jma

An MCP server for Japan Meteorological Agency (気象庁, JMA) data — weather forecasts, warnings and advisories, earthquakes with per-area seismic intensity, tsunami bulletins and volcano alerts. Place names work in kanji, kana or romaji. No API key.

CI License: MIT Node.js MCP Compatible

English · 日本語

Why

JMA publishes its forecasts, warnings and earthquake data as JSON behind www.jma.go.jp/bosai, but the feeds are keyed by 6–7 digit area codes, use numeric weather and warning codes, and split one earthquake over several bulletins. This server does that legwork so an LLM can answer "Is there a warning in Sapporo?" or "How strong was this morning's quake in Chiba?" with one tool call:

  • Place names in any script — 渋谷区, しぶや, シブヤ, Shibuya and 1311300 all resolve through JMA's own area.json.

  • Codes decoded — weather codes get JMA's Japanese and English labels; warning codes become names, severity and alert level.

  • The 2026-05-28 warning system — JMA moved warnings to a new feed (warning/data/r8/) with the new 危険警報 (urgent warning, alert level 4) tier. This server reads the new feed and merges its per-type bulletin streams into "what is in effect now".

  • Polite client — responses are cached (forecasts 10 min, warnings 2 min, quake and tsunami lists 1 min, area tables 24 h), concurrent identical requests share one fetch, and every request sends User-Agent: mcp-server-jma/<version> (+https://github.com/b84330808/mcp-server-jma).

Related MCP server: Japanese Weather MCP

Tools

Tool

What it returns

jma_find_area

Ranked JMA areas for a place name (kanji, kana, romaji) or code: level (office / class10 / class15 / class20 / center), hierarchy path, and the office_code used for forecasts and warnings.

jma_get_forecast

Today + 2 days per sub-region (weather text, English label, wind, waves, 6-hour precipitation chance %, morning low / daytime high °C per station) and the 7-day outlook (weather, precipitation %, reliability A/B/C, low/high °C with likely range, climate normals), plus the forecaster's written overview.

jma_get_warnings

Warnings and advisories in effect now: name (ja/en), severity (advisory / warning / urgent_warning / emergency_warning), alert level 2–5 where JMA assigns one, extra hazards (竜巻, ひょう …), affected sub-regions and municipalities, and JMA's headline.

jma_list_earthquakes

Recent quakes, newest first: origin time, epicenter (ja/en, lat/lon, depth km), magnitude, maximum JMA seismic intensity (震度), per-prefecture maxima, and a detail_id. Filters: min_intensity, min_magnitude, since_hours, limit.

jma_get_earthquake

One quake in full: hypocenter, magnitude, JMA's tsunami assessment (ja/en), intensity by prefecture → region → municipality (strongest first), and optional per-station readings with coordinates.

jma_get_tsunami

Latest tsunami bulletin per recent event: in effect or not, highest level (major_warning / warning / advisory / forecast), coastal areas grouped by category with expected max height (m) and first-wave arrival, observations, and the source earthquake.

jma_get_volcano_warnings

Volcanoes in JMA's eruption-warning feed: Volcanic Alert Level 1–5, status wording, raised/lowered, affected municipalities, actions and coordinates. Optional name filter (桜島, Sakurajima).

Every response is JSON shaped like { "success": true, "data": …, "note": …, "attribution": "出典：気象庁ホームページ …" }. Errors come back as { "success": false, "error": { "code", "message" } } with codes such as AREA_NOT_FOUND, AREA_TOO_BROAD (e.g. 北海道 — the error lists the forecast offices to pick from), EVENT_NOT_FOUND, NOT_FOUND, UPSTREAM_TIMEOUT and UPSTREAM_ERROR.

Units. Temperatures °C · precipitation chance % · 7-day precipitation normals mm · depth km · tsunami height m · magnitude is JMA magnitude (Mj) · seismic intensity is the JMA 震度 scale (1–4, 5- 5弱, 5+ 5強, 6- 6弱, 6+ 6強, 7), not Mercalli · all times are JST (+09:00).

Live output

Real output of npm run smoke (the built server over stdio, against the live JMA endpoints) on 2026-10-27 16:12 JST. It prints a compact summary of each tool result; npm run smoke -- --full prints the full JSON.

### jma_find_area {"query":"さっぽろ","limit":3} (168 ms)
[
  {
    "code": "0110000",
    "level": "class20",
    "name": "札幌市",
    "name_en": "Sapporo City",
    "office_code": "016000",
    "path": "北海道地方 > 石狩・空知・後志地方 > 石狩地方 > 石狩中部 > 札幌市"
  }
]

### jma_get_forecast {"area":"Shibuya"} (49 ms)
{
  "office": {
    "code": "130000",
    "name": "東京都"
  },
  "resolved": {
    "query": "Shibuya",
    "code": "1311300",
    "level": "class20",
    "name": "渋谷区",
    "name_en": "Shibuya City",
    "path": "関東甲信地方 > 東京都 > 東京地方 > ２３区西部 > 渋谷区"
  },
  "report_datetime": "2026-10-27T11:00:00+09:00",
  "short_term": [
    {
      "name": "東京地方",
      "days": [
        "2026-10-27 くもり 時々 晴れ 所により 昼前 雨 (Mostly Cloudy)",
        "2026-10-28 晴れ 夜 くもり (Clear)",
        "2026-10-29 くもり 時々 晴れ (Mostly Cloudy)"
      ],
      "precipitation_chance": [
        "10-27T12:00 10%",
        "10-27T18:00 10%",
        "10-28T00:00 0%",
        "10-28T06:00 0%",
        "10-28T12:00 0%",
        "10-28T18:00 0%"
      ]
    }
  ],
  "temperatures": [
    {
      "station_code": "44132",
      "station": "東京",
      "days": [
        {
          "date": "2026-10-27",
          "min_c": null,
          "max_c": 22
        },
        {
          "date": "2026-10-28",
          "min_c": 15,
          "max_c": 20
        }
      ]
    }
  ],
  "weekly": [
    {
      "name": "東京地方",
      "days": [
        "2026-10-28 Clear -%",
        "2026-10-29 Mostly Cloudy 30%",
        "2026-10-30 Cloudy, Occasional Scattered Showers 50% C",
        "2026-10-31 Cloudy 40% B",
        "2026-11-01 Partly Cloudy 20% A",
        "2026-11-02 Cloudy 40% B",
        "2026-11-03 Mostly Cloudy 30% A"
      ]
    }
  ]
}

### jma_get_warnings {"area":"東京都"} (30 ms)
{
  "office": {
    "code": "130000",
    "name": "東京都"
  },
  "latest_report_datetime": "2026-10-27T16:04:00+09:00",
  "in_effect": [
    {
      "code": "14",
      "name": "雷注意報",
      "name_en": "Thunderstorm Advisory",
      "severity": "advisory",
      "alert_level": null,
      "region_count": 1,
      "municipality_count": 1
    },
    {
      "code": "15",
      "name": "強風注意報",
      "name_en": "Gale Advisory",
      "severity": "advisory",
      "alert_level": null,
      "region_count": 3,
      "municipality_count": 14
    },
    {
      "code": "16",
      "name": "波浪注意報",
      "name_en": "High Wave Advisory",
      "severity": "advisory",
      "alert_level": null,
      "region_count": 3,
      "municipality_count": 14
    }
  ],
  "headlines": [
    {
      "report_datetime": "2026-10-27T16:04:00+09:00",
      "text": "東京地方、伊豆諸島北部、伊豆諸島南部では、強風に注意してください。"
    },
    {
      "report_datetime": "2026-10-27T16:04:00+09:00",
      "text": "東京地方、伊豆諸島北部、伊豆諸島南部では、高波に注意してください。"
    },
    {
      "report_datetime": "2026-10-27T16:04:00+09:00",
      "text": "小笠原諸島では、急な強い雨や落雷に注意してください。"
    }
  ],
  "note": "3 kind(s) of warning/advisory in effect for 東京都."
}

### jma_list_earthquakes {"limit":3} (21 ms)
[
  {
    "origin_time": "2026-10-27T15:32:00+09:00",
    "epicenter": {
      "name": "熊本県熊本地方",
      "name_en": "Kumamoto Region, Kumamoto Prefecture",
      "latitude": 32.5,
      "longitude": 130.6,
      "depth_km": 10
    },
    "magnitude": 3,
    "max_intensity": {
      "value": "2",
      "ja": "震度2",
      "en": "2"
    },
    "detail_id": "20261027153541_20261027153247_VXSE5k_1.json"
  },
  {
    "origin_time": "2026-10-27T09:25:00+09:00",
    "epicenter": {
      "name": "福島県沖",
      "name_en": "Off the Coast of Fukushima Prefecture",
      "latitude": 37.4,
      "longitude": 141.5,
      "depth_km": 60
    },
    "magnitude": 4.6,
    "max_intensity": {
      "value": "3",
      "ja": "震度3",
      "en": "3"
    },
    "detail_id": "20261027092912_20261027092519_VXSE5k_1.json"
  },
  {
    "origin_time": "2026-10-27T08:54:00+09:00",
    "epicenter": {
      "name": "熊本県天草・芦北地方",
      "name_en": "Amakusa and Ashikita Region, Kumamoto Prefecture",
      "latitude": 32.3,
      "longitude": 130.4,
      "depth_km": 10
    },
    "magnitude": 2.1,
    "max_intensity": {
      "value": "1",
      "ja": "震度1",
      "en": "1"
    },
    "detail_id": "20261027085717_20261027085407_VXSE5k_1.json"
  }
]

### jma_get_earthquake {"detail_id":"20261027153541_20261027153247_VXSE5k_1.json"} (12 ms)
{
  "title": "震源・震度情報",
  "origin_time": "2026-10-27T15:32:00+09:00",
  "epicenter": {
    "name": "熊本県熊本地方",
    "name_en": "Kumamoto Region, Kumamoto Prefecture",
    "latitude": 32.5,
    "longitude": 130.6,
    "depth_km": 10
  },
  "magnitude": 3,
  "max_intensity": {
    "value": "2",
    "ja": "震度2",
    "en": "2"
  },
  "tsunami_comment": {
    "ja": "この地震による津波の心配はありません。",
    "en": "This earthquake poses no tsunami risk."
  },
  "intensity_by_prefecture": [
    {
      "name": "熊本県",
      "max_intensity": "2",
      "cities": [
        "八代市 震度2",
        "熊本西区 震度1",
        "宇城市 震度1"
      ]
    }
  ]
}

### jma_get_tsunami {"limit":1} (26 ms)
{
  "any_warning_in_effect": false,
  "any_in_effect": false,
  "bulletins": [
    {
      "title": "津波予報",
      "report_datetime": "2026-10-10T03:37:00+09:00",
      "valid_until": "2026-10-11T20:00:00+09:00",
      "in_effect": false,
      "highest_level": "forecast",
      "earthquake": {
        "origin_time": "2026-10-10T02:56:00+09:00",
        "epicenter": "中米",
        "epicenter_en": "Central America",
        "latitude": 7.5,
        "longitude": -80.8,
        "depth_km": null,
        "magnitude": 8
      },
      "areas": 28
    }
  ],
  "note": "No tsunami warning or advisory is in effect now."
}

### jma_get_volcano_warnings {"volcano":"桜島"} (17 ms)
[
  {
    "name": "桜島",
    "name_en": "Sakurajima",
    "alert_level": 3,
    "status": "レベル3(入山規制)",
    "change": "引下げ",
    "warning_in_effect": true,
    "report_datetime": "2022-07-27T20:00:00+09:00"
  }
]

Installation

Claude Desktop

Add this to claude_desktop_config.json (macOS: ~/Library/Application Support/Claude/claude_desktop_config.json, Windows: %APPDATA%\Claude\claude_desktop_config.json):

{
  "mcpServers": {
    "jma": {
      "command": "npx",
      "args": ["-y", "--package=https://github.com/b84330808/mcp-server-jma/releases/download/v0.1.0/mcp-server-jma-0.1.0.tgz", "mcp-server-jma"]
    }
  }
}

Restart Claude Desktop. The URL is the npm pack tarball attached to the v0.1.0 release; npx installs it and its runtime dependencies. Once the package is on npm, "args": ["-y", "mcp-server-jma"] works too. (npx github:b84330808/mcp-server-jma does not work: current npm fails on git installs that need a build step.)

Claude Code

claude mcp add jma -- npx -y --package=https://github.com/b84330808/mcp-server-jma/releases/download/v0.1.0/mcp-server-jma-0.1.0.tgz mcp-server-jma

From source

git clone https://github.com/b84330808/mcp-server-jma.git
cd mcp-server-jma
npm install
npm run build

Then point your client at it:

{
  "mcpServers": {
    "jma": {
      "command": "node",
      "args": ["/absolute/path/to/mcp-server-jma/dist/index.js"]
    }
  }
}

Example prompts

  • 「明日の札幌の天気は？」 / "What's the weather in Naha this week?"

  • "Are there any weather warnings for Shibuya right now?"

  • 「今朝の地震、千葉ではどのくらい揺れた？」

  • "Is there a tsunami warning in effect?"

  • "What is Sakurajima's volcanic alert level?"

Data source and terms

  • Source: 出典：気象庁ホームページ (www.jma.go.jp). Every tool response carries this attribution and a source_url pointing to the matching JMA page; keep it when you show or redistribute the data.

  • JMA content is provided under the 気象庁ホームページ利用規約, which follows the Government of Japan Standard Terms of Use (政府標準利用規約 2.0, compatible with CC BY 4.0). If you edit or process the data, say so and do not present it as JMA's own output.

  • Unofficial endpoints, no SLA. The bosai JSON files are what JMA's own web pages load; they are public but not a documented API. JMA can change or remove them without notice (it did so for warnings on 2026-05-28). If a tool starts returning NOT_FOUND or empty data, check the corresponding page on jma.go.jp and open an issue.

  • This server is not affiliated with or endorsed by JMA. For life-safety decisions, follow JMA, your municipality and broadcast alerts directly.

Endpoints used (all under https://www.jma.go.jp/bosai/):

Data

Path

Cache

Area table

common/const/area.json

24 h

Forecast / overview

forecast/data/forecast/{office}.json, forecast/data/overview_forecast/{office}.json

10 min

Forecast area maps

forecast/const/forecast_area.json, forecast/const/week_area.json

24 h

Warnings (since 2026-05-28)

warning/data/r8/{office}.json

2 min

Earthquakes

quake/data/list.json, quake/data/{detail_id}

1 min / 24 h

Tsunami

tsunami/data/list.json, tsunami/data/{file}

1 min / 24 h

Volcanoes

volcano/data/warning.json, volcano/const/volcano_list.json

5 min / 24 h

Development

npm install
npm run lint     # type check
npm test         # unit tests on recorded fixtures (tests/fixtures, recorded 2026-10-27)
npm run build
npm run smoke    # live run against JMA (network)

Tests never touch the network: tests/helpers.ts serves the recorded JMA responses in place of axios.get.

Project structure

src/
├── index.ts         # stdio entry point
├── server.ts        # tool definitions and dispatch
├── http.ts          # fetch + cache + User-Agent, error mapping
├── areas.ts         # area.json index and place-name resolver
├── forecast.ts      # 3-day + weekly forecast parser
├── warnings.ts      # r8 warning feed → what is in effect
├── quake.ts         # earthquake list and detail
├── tsunami.ts       # tsunami bulletins
├── volcano.ts       # volcano warnings
├── codes.ts         # warning codes, prefectures, intensity scale
├── weatherCodes.ts  # JMA weather code labels (ja/en)
└── text.ts          # text, number, time and romaji helpers

License

MIT — see LICENSE. The data itself belongs to JMA; see Data source and terms.

Available Tools

7 tools
jma_find_areaA

Looks up Japan Meteorological Agency (JMA, 気象庁) area codes for a place in Japan. Accepts kanji (東京都, 札幌市, 渋谷区), kana (さっぽろ, シブヤ), romaji/English (Sapporo, Shibuya, Tokyo) or a JMA code. Returns ranked matches with their level (office = prefecture-level forecast district 府県予報区; class10 = sub-region 一次細分区域; class15 = local area; class20 = municipality 市区町村; center = regional block such as 北海道地方), the hierarchy path, and office_code, the code jma_get_forecast and jma_get_warnings use. You can usually pass a place name straight to those tools; call this first when a name is ambiguous (府中 exists in Tokyo and Hiroshima) or to show the user which area was meant. No API key needed.

Inputs: query (required), limit.

jma_get_earthquakeA

Full Japan Meteorological Agency (JMA) report for one earthquake: hypocenter (name, latitude/longitude, depth in km), JMA magnitude, JMA's tsunami assessment in Japanese and English (e.g. 'This earthquake poses no tsunami risk.'), and observed seismic intensity (震度) by prefecture → region → municipality, strongest first. Set include_stations to also get each seismometer's reading and coordinates (large quakes have hundreds). Identify the quake with detail_id from jma_list_earthquakes, or with its 14-digit event_id.

Inputs: event_id, detail_id, include_stations.

jma_get_forecastA

Weather forecast from the Japan Meteorological Agency (JMA, 気象庁) for a place in Japan. Returns: today and the next 2 days per sub-region (weather text, wind, wave height in metres, precipitation chance in % for each 6-hour block, morning low and daytime high in °C at observation stations); a 7-day outlook (weather, precipitation chance %, reliability A=high/B=fair/C=low, low/high °C with the likely range, 30-year climate normals); and the forecaster's written overview. JMA issues forecasts per prefecture-level office around 05:00, 11:00 and 17:00 JST. Naming a municipality narrows the result to its sub-region. All times are JST (+09:00). Weather, wind and wave text is Japanese as JMA issued it; weather_en is an English label for each weather code.

Inputs: area (required).

jma_get_tsunamiA

Tsunami warnings, advisories and forecasts (津波警報・注意報・予報) from the Japan Meteorological Agency (JMA). Returns the latest bulletin for each recent tsunami-related event, newest first, with: whether it is still in effect; its highest level (major_warning 大津波警報 > warning 津波警報 > advisory 津波注意報 > forecast 津波予報, i.e. slight sea-level change with no damage expected); coastal forecast areas grouped by category with expected maximum height in metres and first-wave arrival time (JST); observed tsunami heights if any; and the source earthquake (which may be far from Japan). any_warning_in_effect=false means no tsunami warning or advisory is active now.

Inputs: limit.

jma_get_volcano_warningsA

Volcanic eruption warnings (噴火警報) from the Japan Meteorological Agency (JMA). Lists volcanoes in JMA's current eruption-warning feed with their Volcanic Alert Level 1–5 (噴火警戒レベル), JMA's status wording (e.g. レベル２（火口周辺規制） = Level 2, do not approach the crater; 周辺海域警戒 = stay clear of surrounding waters), whether the level was raised (引上げ) or lowered (引下げ), the affected municipalities, required actions and coordinates. Optional volcano filter by Japanese or romaji name (桜島, Sakurajima, 阿蘇, Aso) or JMA volcano code. A volcano that is not in the feed has no eruption warning in effect.

Inputs: volcano.

jma_get_warningsA

Weather warnings and advisories (気象警報・注意報) in effect now, from the Japan Meteorological Agency (JMA), for a place in Japan. Uses the warning system JMA introduced on 2026-05-28: advisory 注意報 < warning 警報 < urgent warning 危険警報 < emergency warning 特別警報; heavy rain, landslide and storm surge also carry an alert level 2–5 (警戒レベル). Returns the distinct warnings in effect (severity, alert level, how many sub-regions and municipalities), each affected area with its warnings and extra hazards (e.g. 竜巻 tornado, ひょう hail, うねり swell), and JMA's Japanese headline text. An empty in_effect list means no warning or advisory is in effect for that area. Naming a municipality narrows the result to it.

Inputs: area (required).

jma_list_earthquakesA

Recent earthquakes in and around Japan from the Japan Meteorological Agency (JMA) feed, newest first (the feed covers roughly the last few weeks). Each item: origin time (JST), epicenter name in Japanese and English with latitude/longitude and depth in km, JMA magnitude (Mj), maximum seismic intensity on the JMA 震度 scale (1, 2, 3, 4, 5- = 5弱, 5+ = 5強, 6- = 6弱, 6+ = 6強, 7; this is not the Mercalli scale), maximum intensity per prefecture, and a detail_id for jma_get_earthquake. Use the filters to find significant quakes, e.g. min_intensity '4' or min_magnitude 5.

Inputs: limit, since_hours, min_intensity, min_magnitude.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

Loading tool schema changelog…

    Deploy Server
    One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

    TDQS

    A4.3/5.0

    Scored across 7 tools

    Disambiguation5/5

    Each tool targets a distinct JMA data product: area lookup, forecast, weather warnings, earthquake list, earthquake detail, tsunami, and volcano warnings. The list/get pair for earthquakes follows a clear convention, and the three hazard tools (warnings, tsunami, volcano) are unambiguous because each names a different hazard type. No two tools appear interchangeable.

    Naming Consistency5/5

    Every tool uses the same jma_ prefix followed by a verb_noun pattern (find_area, get_forecast, list_earthquakes, get_earthquake, get_tsunami, get_volcano_warnings). The list vs get distinction is applied consistently and predictably.

    Tool Count5/5

    Seven tools is well within the sweet spot for a domain-specific data server. Each tool corresponds to a genuine, distinct JMA dataset with no filler or trivially wrapped endpoints.

    Completeness4/5

    The surface covers area resolution, forecasts, weather warnings, earthquakes (both list and detail), tsunami, and volcano warnings — strong lifecycle coverage for hazard monitoring. Minor gaps remain, such as current/observed conditions (AMeDAS) and typhoon tracks, but agents can work around these for most JMA use cases.

    Maintenance

    ActivityMaintained
    ResponsivenessNo recent community issues

    Resources

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