JMA Data MCP

Get Historical Weather

get_historical_weather

Read-onlyIdempotent

Retrieves historical weather observations for a specific station, date, and time in Japan, covering approximately the past one to two weeks.

Instructions

Get historical weather data for a specific date and time.

Data is available for approximately the past 1-2 weeks.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "station_code": "<station_code>",
      "target_datetime": "<target_datetime>"
    },
    "name": "get_historical_weather"
  }
}

Input Schema

Name	Required	Description	Default
`station_code`	Yes	Station code (e.g., '44132' for Tokyo)
`target_datetime`	Yes	Target datetime in ISO format (e.g., '2025-12-01T12:00:00') or 'YYYY-MM-DD HH:MM' format. Time is in JST.

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedv0.2.1May 1, 2026

addedInput schema / additionalProperties
```
Added value: +false
```
addedInput schema / properties / station_code / description
```
Added value: +"Station code (e.g., '44132' for Tokyo)"
```

addedInput schema / properties / target_datetime / description

Added value: +"Target datetime in ISO format (e.g., '2025-12-01T12:00:00')\n             or 'YYYY-MM-DD HH:MM' format. Time is in JST."

First observedDec 19, 2025

TDQS

A3.6/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds one genuinely new behavioral fact — the ~1-2 week data retention window — but says nothing about behavior for out-of-range dates (error vs. empty result) or the JST assumption baked into the schema.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, zero redundancy, and the core action is front-loaded before the availability caveat. Nothing could be cut without losing information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need no explanation, and both parameters are fully documented in the schema. What's missing is the edge-case behavior for dates outside the stated window — the one ambiguity an agent is likely to hit in practice.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%: both station_code (with example) and target_datetime (ISO/`YYYY-MM-DD HH:MM`, JST) are already documented. The description adds no parameter-level meaning beyond the schema, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource ("get historical weather data") with a scoping constraint (specific date and time). The word "historical" reasonably separates it from get_current_weather and get_forecast, but no sibling is named explicitly the way a top-tier definition would do.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

"Data is available for approximately the past 1-2 weeks" frames the viable window and implicitly rules out far-past queries, which is useful. However, it never tells the agent when to pick this over get_weather_time_series or get_current_weather, and gives no guidance on what to do when the requested date falls outside that window.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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