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

Annotations already establish readOnly/non-destructive/closed-world, so safety is covered. The description adds real behavioral value by disclosing that the response is deliberately trimmed to only id, name and nextFiscalYearEnd — important since there is no output schema to reveal this.

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?

Two sentences, no filler: the first gives purpose plus return shape, the second gives the prerequisite and the sibling routing. Purpose is front-loaded.

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 single-parameter read tool with no output schema, the description covers what it does, how to obtain the ID, what comes back, and where to go for adjacent data. Only minor gaps (e.g., behavior when the ID is inaccessible or invalid) remain, which is acceptable for this scope.

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 single parameter is fully documented in the schema. The description reinforces 'by ID' and points to list-companies as the ID source, matching but not exceeding the schema's own note. Baseline 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 ('Get one company by ID') and immediately delimits the scope with the exact fields returned. It is cleanly distinguishable from sibling list/get tools without opening any 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 an explicit prerequisite ('Use list-companies first to find the IDs of companies the user can access') and names two alternatives (get-directors-shareholders, get-corporate-subsidiaries) with the condition that routes to them (ownership and structure). Nothing 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.