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日本の給与・社会保険・労働法

by io.github.kishida-devil

源泉徴収税額(月額表・日額表・電算機計算の特例)

calculate_withholding_tax

Income tax to withhold from a payment, from the National Tax Agency tables. The taxable amount is pay AFTER social insurance has been deducted, not gross.

Pick the table with period: "monthly" for 月額表, "daily" for 日額表. The daily table has a third column, 丙, which applies to work engaged by the day and takes no dependant adjustment at all. Use method: "computer" for the 電算機計算の特例 formula, which payroll software may use instead of the table and can differ by a few yen.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
columnNo甲/乙, plus 丙 for the daily table only. Defaults to 甲.
methodNo"computer" selects the statutory formula method. Monthly only. Defaults to table.
periodNoDefaults to monthly.
spouseNoOnly for method "computer": whether a 源泉控除対象配偶者 is claimed. The formula method deducts 31,667 yen a month for one, which the monthly table folds into its columns instead. Ignored by the table methods.
dependantsNo
taxable_amountYesPay after social insurance, in yen.

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

  1. First observed

TDQS

A4.3/5.0
Behavior4/5

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

With no annotations, the description carries the full burden and discloses important behaviors: taxable amount is after social insurance, the daily 丙 column makes no dependant adjustment, and the computer method can differ by a few yen. It does not describe the return format, but this is a pure calculation tool with no side effects.

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 dense paragraphs front-load the core purpose and most critical caveat before the selection instructions. Every sentence provides useful guidance without repetition.

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

Completeness3/5

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

The description is strong on period/method selection and the after-social-insurance rule, but it leaves out the meaning of 甲 vs 乙, the semantics of dependants, and what the tool returns. With no output schema and no annotations, those are notable gaps for a six-parameter tax tool.

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

Parameters4/5

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

Schema coverage is 83%, so the baseline is 3, but the description adds value by clarifying the after-social-insurance taxable amount, the daily-table 丙 exception, and the possible difference between table and computer methods. The dependants parameter is still not explained.

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?

The description identifies a specific operation and resource: calculating income tax to withhold from a payment using National Tax Agency tables. This clearly separates it from payroll siblings such as bonus or year-end adjustment calculations.

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?

It gives explicit selection instructions for period (monthly vs daily) and method (table vs computer), including when the computer formula applies. It does not name sibling tools to exclude, so it misses explicit when-not-to-use guidance.

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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TDQS

A3.8/5.0
Disambiguation4/5

Most tools have distinct, well-defined jobs—payroll calculations, revision judgments, eligibility checks, and data lookups are clearly separated. The main remaining risk is among the standard-remuneration judgment tools and the batch/singleton pairs, but their descriptions are detailed enough to prevent serious misselection.

Naming Consistency3/5

There is a reasonably recognizable pattern with calculate_, judge_, check_, get_, and validate_ groups. However, several noun-phrase names (business_days, consumption_tax, national_insurance, commuting_allowance_exemption) and overlapping verb choices (decide_ vs judge_ vs check_) prevent a fully consistent verb_noun convention.

Tool Count2/5

At 30 tools, the surface is materially larger than the 3–15 range that keeps an agent's selection burden low. Batch variants and three separate standard-remuneration revision tools add complexity, and although the domain is broad, the count feels heavy for an assistant to choose from confidently.

Completeness4/5

The core workflows are well covered: monthly pay, bonuses, overtime, standard-remuneration determination, year-end adjustment, resident tax, leave, worker classification, and invoice validation. Gaps exist around statutory benefit payments such as sickness or maternity allowances and retirement-specific processing, but most payroll and social insurance tasks can be completed without dead ends.

Resources