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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered elsewhere. The description adds which data categories come back, which is genuinely useful, but it says nothing about not-found behavior or error handling for an invalid number.

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?

A single front-loaded sentence with no filler; the resource and the returned field categories are stated up front and nothing is restated from the schema 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 simple two-parameter read-only lookup with full schema coverage and rich annotations, the description covers what the tool returns well enough to call it correctly. Only the routing versus search_companies and not-found behavior are left implicit.

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 description coverage is 100%, so both parameters (company_number with accepted formats, locale with its enum and nl default) are already documented in the schema. The description adds only the loose hint that the number is Belgian/KBO, so it meets the baseline without more.

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 ("look up KBO company information") plus the fields returned (address, legal form, NACE codes), which separates it from the sibling lookups on financials, employees, mandates and shareholders. It does not explicitly distinguish itself from search_companies, which is the closest ambiguity.

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?

The lookup framing implies usage — call it with a company number to retrieve profile data — but there is no explicit when-to-use statement, no note that a company number is required rather than a name, and no pointer to search_companies for name-based discovery.

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