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

Annotations already declare read-only, idempotent, non-destructive behavior, so the safety profile is covered. The description adds genuinely useful behavior beyond that: full-fiscal-year figures as filed, currency/unit attached to each amount, amounts with undeterminable units returned 'unresolved, never guessed', and 'found:false' for filers without structured data. It also notes the _apiKey requirement, though the schema calls that parameter optional and defaulted, a small inconsistency.

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?

Front-loads the resource and the returned fields, then moves to data-integrity guarantees and an example. It is dense but every clause carries information; only the 'Requires a free EDINET Subscription-Key via _apiKey' sentence is questionable given the schema marks the key as optional.

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?

An output schema exists, so return structure need not be spelled out, and the description still covers the things the schema cannot: accounting standard variation, currency/unit resolution policy, and the not-found case. For a four-parameter read tool with full schema coverage, nothing an agent needs in order to call it correctly 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 coverage is 100%, with each of the four parameters individually documented, including the fiscal_year convention and default. The description adds no additional parameter meaning beyond repeating an example using sec_code, so the baseline of 3 applies.

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 — 'Reported annual financials ... from its EDINET annual securities report' — and enumerates the exact figures returned (net sales, operating income, net income attributable to owners of the parent, total assets, net assets). This clearly separates it from sibling filing tools like edinet_list_filings and edinet_search_filers, which deal with filings and filers rather than reported figures.

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?

Provides a concrete example call and explains the fallback ('found:false' when no structured data), which implies when the tool is appropriate. However, it never explicitly says when to prefer this over edinet_company_filings or the other Edinet siblings, so the routing decision is left to inference.

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