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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds meaningful cost/behavior context: EDINET has no company-search endpoint, so the call walks daily filing lists and filters rows, implying multiple upstream requests and latency. It also discloses the auth requirement ('free EDINET Subscription-Key via _apiKey') and result ordering, which the annotations do not convey.

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?

Four short sentences, front-loaded with the scope and capped by the date-range limit, followed by the prerequisite and only then the example. Nothing is repeated and every sentence carries selection-relevant information.

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 filtered-list tool with no output schema, the definition covers scope, ordering ('newest first'), prerequisite resolution, and auth. The return shape is only gestured at ('keeps that filer's rows'), so an agent must infer the per-filing fields, which is the one remaining gap.

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 coverage is 100%, so the schema already documents all five parameters including the edinet_code vs sec_code alternative; the description adds only the worked example call. It generates useful value by showing the canonical three-parameter invocation, but it says nothing about when to prefer sec_code over edinet_code, so the baseline 3 holds.

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 description names a specific verb+resource+scope: 'All EDINET filings by one Japanese company over a date range of up to 31 days, newest first.' This differs unmistakably from siblings like edinet_list_filings (unfiltered daily lists) and edinet_search_filers (which resolves a company), so an agent can select it 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.

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

It gives an explicit prerequisite sequence — 'Identify the company with edinet_search_filers first' — and states the 31-day window constraint, which governs when the tool can even be called. It stops short of explicitly naming edinet_list_filings as the alternative for unfiltered retrieval, so usage is clear but not fully exclusionary.

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