Mart402 Japan Statutory

Jp Social Insurance

jp_social_insurance

Idempotent

Monthly social insurance premiums from the official Kyokai-Kenpo grade table (FY2026). $0.01/call. Deterministic, cites primary sources; errors and unverified rules are never billed. Choose this when you only need the monthly social insurance premiums for a given monthly remuneration (official grade table); no tax is computed - for take-home pay use jp_payroll_net.

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": {
      "monthly_remuneration_yen": "<monthly_remuneration_yen>",
      "prefecture": "<prefecture>"
    },
    "name": "jp_social_insurance"
  }
}

Input Schema

Name	Required	Description
`age`	No	Age in years (selects care-insurance and other age-gated rules)
`as_of`	No	Calculation reference date YYYY-MM-DD (default today); selects the rules version
`x_payment`	No	Optional: base64 X-PAYMENT header value (x402 exact scheme, USDC on Base mainnet). Omit it to receive the payment requirements (accepts[] + docs) for this call without being charged.
`prefecture`	Yes	Prefecture (romaji or Japanese), e.g. 'Tokyo'
`monthly_remuneration_yen`	Yes	Monthly remuneration in yen (grade table lookup)

Output Schema

Name	Required	Description
`body`	Yes	JSON body of the underlying call (see /samples/{product} for each product's shape)
`status`	Yes	HTTP status of the underlying call (200 result, 402 payment terms, 4xx input error)
`how_to_pay`	No
`receipt_id`	No	set on paid results; free re-fetch via get_receipt
`payment_required`	No	true when status is 402: body holds x402 payment terms, not a result. Pay and call again with x_payment

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 20, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Goes well beyond the annotations by disclosing per-call pricing ($0.01/call), the billing guarantee (errors and unverified rules are never billed), determinism, and primary-source citation behavior. This also contextualizes the readOnlyHint=false annotation, which would otherwise look surprising for a pure calculation tool.

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?

Front-loaded with the what and the data source, then pricing, then the sibling routing rule — no wasted sentences. Slightly dense with parentheticals, but every clause carries information.

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?

For a deterministic, output-schema-backed calculation tool, the description covers source, scope, cost model, and alternative routing; return values need not be explained given the output schema. Nothing needed to invoke it 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 100%, so all five parameters (including the x_payment payment flow and age-gated rules) are already documented in the schema. The description adds only the framing that remuneration is a grade-table lookup, which the schema already says; 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?

States a specific resource (monthly social insurance premiums) with a specific source (official Kyokai-Kenpo grade table, FY2026), and explicitly bounds the scope to premiums only, excluding tax. An agent can distinguish it from jp_payroll_net without opening either schema.

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 'Choose this when you only need...' condition plus a named alternative and its selection rule ('for take-home pay use jp_payroll_net'). Both the when and the when-not are stated.

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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