japan-data-mcp

list_japan_datasets

Read-onlyIdempotent

Discover available Japanese official dataset IDs, titles, record counts, and coverage years across 155 datasets. Use this first when you need a dataset_id before searching rows or inspecting columns.

Instructions

Discover and list available dataset IDs, titles, record counts, and coverage years across all 155 official Japanese datasets in Japan Official Data Megabank (demographics, real_estate, procurement, companies, medical, renewable_energy, grid_capacity, etc.). WHEN TO USE: Call this tool first when you do not know the exact 'dataset_id' to query. NEXT STEP: Pass a discovered 'dataset_id' to 'describe_japan_dataset' to inspect columns, or directly to 'search_japan_official_data' to fetch rows. WHEN NOT TO USE: Do not use this tool to fetch actual data rows (use 'search_japan_official_data' instead) or B2B bulk product bundles (use 'list_flagship_b2b_bundles').

Input Schema

TableJSON Schema

Name	Required	Description	Default
`limit`	No	Maximum number of dataset catalog entries to return (1 to 155, default: 25).
`query`	No	Optional case-insensitive keyword filter in English or Japanese to match dataset IDs or titles (e.g., 'procurement', 'hospital', 'solar', '入札', '医療'). If omitted, returns the top catalog entries.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`total`	No	Total number of datasets available in the catalog.
`datasets`	No	List of matching dataset metadata objects containing dataset_id, title_en, records, and coverage.

Schema Changelog

Changes observed during successful MCP inspections.

Changed7 schema fields changedv1.0.4Oct 15, 2026

addedInput schema / additionalProperties
```
Added value: +false
```

changedInput schema / properties / limit / description

Previous value: -"Maximum number of datasets to return (default: 25, max: 155)."New value: +"Maximum number of dataset catalog entries to return (1 to 155, default: 25)."

addedInput schema / properties / limit / maximum
```
Added value: +155
```
addedInput schema / properties / limit / minimum
```
Added value: +1
```

changedInput schema / properties / query / description

Previous value: -"Optional keyword in English or Japanese (e.g. 'procurement', 'hospital', 'solar', '入札', '医療')."New value: +"Optional case-insensitive keyword filter in English or Japanese to match dataset IDs or titles (e.g., 'procurement', 'hospital', 'solar', '入札', '医療'). If omitted, returns the top catalog entries."

addedOutput schema / properties / datasets / description

Added value: +"List of matching dataset metadata objects containing dataset_id, title_en, records, and coverage."

addedOutput schema / properties / total / description

Added value: +"Total number of datasets available in the catalog."

First observedv0.1.0Oct 15, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered and the bar is lower. The description adds genuine context beyond them: the catalog returns metadata only (no rows), spans all 155 official datasets, and the coverage domains it indexes. It stops short of describing pagination/truncation behavior of the limit cap or how the default of 25 is chosen.

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

Conciseness4/5

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

The label-per-function structure (purpose, WHEN TO USE, NEXT STEP, WHEN NOT TO USE) is front-loaded and scannable, and the parenthetical domain list is informative rather than padding. It runs long, but each clause carries routing or scope information that an agent uses.

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

Completeness5/5

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

With an output schema present the return fields need not be explained, and annotations carry the safety profile, so the description's job is routing and scope – both fully delivered. Nothing an agent needs to select or invoke this catalog tool is missing.

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%, so both parameters (limit, query) are already documented in the schema, including the 1-155 range, default and bilingual keyword examples. The description adds no interpretation 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.

Purpose5/5

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

Opens with a specific verb and resource ('Discover and list available dataset IDs, titles, record counts, and coverage years') and scopes it precisely to the 155 datasets in the Megabank, even enumerating the covered domains. An agent can immediately distinguish this catalog tool from describe_/search_/SQL siblings.

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

Usage Guidelines5/5

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

Explicit WHEN TO USE ('call this tool first when you do not know the exact dataset_id'), a NEXT STEP routing to describe_japan_dataset or search_japan_official_data, and a WHEN NOT TO USE that names both the row-fetching sibling and list_flagship_b2b_bundles. When/when-not/alternative routing is fully specified.

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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