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

With readOnlyHint already declaring the safety profile, the description adds genuinely useful behavioral context: dual upstream sources (TDnet same-day vs EDINET), row-level provenance (doc_id + EDINET URL), and non-obvious derivation rules for revenue, grossProfit and operatingIncome under Japanese GAAP. It does not cover ordering beyond the schema, error/empty behavior, or rate limits, so it stops short of a 5.

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

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

The purpose and the GAAP caveats are correctly front-loaded, but every sentence is duplicated verbatim in Japanese, including the ISO 8601 datetime explanation and its 'add 9 hours' note, roughly doubling length without adding information. The core content is worthwhile; the structure is padded.

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

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

For a financial-statement tool with no output schema, the description covers the hard parts an agent would otherwise get wrong: the retailer/operating-revenue revenue formula, the operatingIncome derivation, and timestamp conventions. It omits the reporting units/currency scale of the figures, which is a meaningful gap for a numeric tool, and says nothing about how rows are ordered beyond the schema's 'newest first'.

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

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

Schema description coverage is 100%, so symbol, limit and the period enum are already fully documented, and the description adds no parameter-specific meaning. The formulas it cites reference output fields (netSales, otherOperatingRevenue, operatingGrossProfit) rather than input semantics, so it neither helps nor hurts parameter interpretation.

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

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

The opening line 'Income statement (P/L) history' gives a specific verb-free but unambiguous resource and scope, and the source detail (TDnet 決算短信 / EDINET) further pins down what data this returns. It is clearly distinguishable from get_balance_sheet and get_cash_flow by resource, but it never explicitly names a sibling or states how it differs from get_full_financial_statement.

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

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

Usage is only implied by the resource name — an agent can infer 'use this for P/L time series.' There is no explicit when-to-use/when-not guidance, no mention of when to prefer get_full_financial_statement or get_xbrl_facts, and no stated prerequisites for the symbol.

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