Ask Japan

Instant quote for buying in Japan

quote_purchase

Read-onlyIdempotent

Instant cost estimate to buy an item sold in Japan and ship it: item price (from the shop page the user or agent found), our fee (10%, minimum JPY 2,000) and shipping estimated from Japan Post's official EMS table. Read-only: it does not order or charge anything.

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": {
      "item_price_jpy": "<item_price_jpy>",
      "ship_to_country": "<ship_to_country>"
    },
    "name": "quote_purchase"
  }
}

Input Schema

Name	Required	Description
`item_url`	No	Product page URL in Japan (Rakuten, Amazon.co.jp, brand store, etc.)
`quantity`	No
`item_name`	No	Product name
`item_price_jpy`	Yes	Price per unit in JPY, tax included, as shown on the shop page
`ship_to_country`	Yes	ISO 2-letter country code of the destination, e.g. US, TW, CN; JP for Japan
`estimated_weight_kg`	No	Item weight in kg if known (default 1.0)
`seller_shipping_jpy`	No	Shop's shipping to our address in Japan, if any

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 13, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint false, and closed-world, so safety is partly covered; the description still adds real behavior the annotations cannot convey, namely the pricing model (10% fee, JPY 2,000 minimum) and the shipping source (Japan Post official EMS table). The explicit 'does not order or charge anything' reinforces rather than contradicts the read-only annotation. Rate limits or quote validity windows are not mentioned.

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?

A single front-loaded sentence: the purpose comes first, followed by the cost components, then the read-only boundary. Every clause carries information an agent needs and there is no restatement of the title or filler.

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 seven parameters, no output schema, and a closed-world quote computation, the description supplies the one thing structured fields cannot: what the returned estimate is composed of. Combined with the 86% schema coverage and existing annotations, nothing an agent needs in order to call this correctly 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 86%, so nearly every parameter is already documented in structured form, including unit price tax treatment, ISO country code, and the default weight of 1.0. The description only echoes the item-price and shipping inputs and adds no format or edge-case semantics beyond the schema. Baseline 3 applies when the schema does the heavy lifting.

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?

States a specific verb and resource (instant cost estimate to buy an item in Japan and ship it) and enumerates the exact components of the estimate: item price, a 10% fee with a JPY 2,000 floor, and shipping from Japan Post's EMS table. That is enough to separate it from ordering or availability-checking siblings without opening the schema.

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

Usage Guidelines4/5

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

The description makes the usage context explicit, including where the price input should come from (the shop page the user or agent found) and the boundary that it does not order or charge anything, which routes the agent away from a purchase action. It stops short of naming any sibling tool or stating exclusion conditions, so it is clear context without explicit alternatives.

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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