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

Annotations already establish that this is read-only, idempotent, and non-destructive, so the description only needs to add context beyond that. It does so by disclosing an auth-dependent output split: free callers get a trace-level preview, while authenticated callers get the full paid dossier. This is useful behavioral context that annotations do not capture.

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 with no filler: the first states the core purpose and accepted identifiers, and the second adds the key access-level behavior. Every sentence earns its place, and the most important information 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 read-only lookup with three optional parameters and an existing output schema, the description covers the essential context: what can be looked up and what different callers receive. It does not specify behavior when no query parameter is supplied, but the output schema and annotations reduce the impact of that gap.

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%; q, name, and query are each documented in the schema, including alias relationships. The description adds no parameter-level detail beyond what the schema already provides, so it stays at the baseline for high schema coverage.

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 ('look up'), a resource ('business entity'), and the accepted identifier types (name, CIF/NIF, EU VAT, LEI). It is immediately clear what the tool does, though it does not explicitly differentiate itself from siblings like search_entities or get_full_dossier.

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 identifier list and 'look up any business entity' imply when the tool should be used, but the description gives no explicit guidance about alternatives or exclusions. With sibling tools such as verify_vat, search_entities, and get_full_dossier, the routing decision 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.