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

Annotations only declare readOnlyHint=true, and the description adds the operationally important behavior: a missing annual report is not an error but a null field, an unknown symbol returns an empty array, and sibling annual-report tools 404 in that case. This null-vs-empty-array-vs-404 distinction is exactly the kind of error-semantics context an agent cannot get from structured fields.

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 English text is front-loaded with the definition and then the failure semantics, with no wasted clauses. The full Japanese restatement doubles the length for the same content, which is a deliberate localization choice but still redundant volume from an agent's perspective.

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?

There is no output schema, and the description compensates by naming the returned field (employeeCount) and enumerating its null and empty-array cases. For a single-parameter read tool, nothing an agent needs in order to call it correctly or interpret the result 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% and the sole parameter is documented with a concrete example, so the baseline is 3. The description still adds meaning beyond the schema by specifying how a bad or unknown symbol resolves (empty array rather than an error), which directly informs how to interpret the symbol argument's failure mode.

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 resource (employee count), a specific source (latest annual securities report), and the consolidation basis (consolidated, falling back to the reporting company alone). It also names the sibling get_workforce and explains how it differs, so an agent can distinguish the two without opening either 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?

Gives clear eligibility context: listed companies with no annual securities report yield employeeCount: null rather than an error, and unknown symbols yield an empty array. It explicitly contrasts this with get_workforce, which 404s in the same situation. It stops short of an explicit 'prefer this tool when...' directive, so it lands at 4 rather than 5.

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