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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered by structured data. The description adds genuine value beyond that: the data source (public KBO register), the returned fields (official name, status, legal form, start date) and the inclusion of a source URL for traceability.

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 tight sentences: the lookup action and identifier come first, the return payload and source second. No filler, no restated title, every clause earns its place.

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, so the description correctly compensates by enumerating the return fields and naming the source register. With annotations covering safety and the schema covering the single parameter, an agent has everything needed to call this correctly.

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% and the schema already specifies the 10-digit format with dots/spaces tolerated plus min/max length, so the description adds only a concrete example (0403.170.701) and the digit count—both of which the schema already carries in substance. Baseline 3 is appropriate.

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 (look up) and a specific resource (Belgian company by KBO/BCE enterprise number), naming the register and the identifier type. Among siblings like vies_validate, iban_validate and the legal/ecli/eurlex lookups, no other tool overlaps this domain, so the agent can route unambiguously.

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 description makes the selection context clear: this is the tool for a company identified by a KBO/BCE enterprise number, and no sibling covers that register. However, it never explicitly states when not to use it (e.g. for VAT-number validation, use vies_validate), so it stops short of explicit alternatives.

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