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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely useful behavior: results are newest-first, sourced from EDINET's CSV of each report, corporate holder names only (others withheld), and figures are as filed with no evaluation or intent commentary. Only pagination/truncation behavior beyond the limit cap is left unstated.

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 core question is front-loaded in the first sentence and the field inventory follows. It is dense but every clause carries information; the middle sentence is long and could be split for readability, which keeps it from a 5.

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?

With an output schema present, return-field detail is not strictly required, yet the description still enumerates the payload and flags data caveats (withheld names, unaudited facts). Combined with read-only annotations, an agent has enough to call it correctly; only sibling disambiguation is missing.

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 all four parameters (issuer, limit, since, holder) are already documented in the schema. The description reinforces ordering ('newest first') and the issuer/holder concept but adds no syntax, defaults, or edge-case meaning 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.

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

States a specific verb-and-resource pair: it returns holding ratios, shares held/outstanding, dates, amendment flags and joint totals from Japanese large shareholding and change reports. An agent can tell it apart from generic filing tools like edinet_company_filings, but the closest sibling, edinet_holdings_tender_offers, is never named or contrasted, leaving ambiguity about which holding-related tool to pick.

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 question framing ('What holding ratios did ... state?'). There is no explicit when-to-use, when-not-to-use, or pointer to an alternative sibling for related queries. The closing caveat ('Facts as filed: not evaluated, nothing about purposes or intentions') limits expectations but is not selection guidance.

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