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

Annotations already declare the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower, and the description still adds substantial interpretation context: the shareholders-vs-supervisoryBoard field distinction and, critically, that derivedEffectiveDate is an INFERRED value (effectiveDateSource: "derived") that must be presented as an estimate, not a register fact. That provenance caveat is exactly the kind of behavior annotations cannot express.

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?

Three sentences, all information-bearing, with the scope statement front-loaded ahead of the field-naming and data-provenance caveats. No restatement of the name, title, or annotations.

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 read-only lookup with an output schema, the description supplies everything the schema cannot: what relation types are in scope, how it differs from the network tool, field-level semantics for shareholders/supervisoryBoard, and the inferred-date caveat. Nothing an agent needs to call or interpret 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%, so ico, country (tie-break warning), and the purpose enum are already fully documented in the schema. The description adds no parameter-level syntax, format, or default information beyond that, so the 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?

The description names a specific verb+resource ('Direct relations of one company') and enumerates exactly what is returned: statutory officers, owners, parents, subsidiaries, M&A events. The phrase 'without traversing the wider graph' implicitly separates it from the graph-traversal sibling (get_company_network), so an agent can route 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?

It gives clear selection context — use this for one company's direct ties rather than the wider network — which is enough to choose it over get_company_network. It stops short of naming that alternative explicitly or stating when a different tool (e.g. get_company_details, advanced_search) would be preferred.

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