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

Annotations only cover read-only/non-destructive safety; the description adds the material behavior: confidential register requiring a signed contract, two distinct refusal modes (contract_required, tier_restricted) both at no cost, and a 2-credit price. That is exactly the context an agent needs before calling.

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?

Front-loads purpose and return fields, then prerequisites, alternatives, cost, and error handling in a sensible order with no filler. It is long, but each sentence carries decision-relevant information for a paid, access-gated lookup.

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?

No output schema exists, yet the description enumerates the returned attributes and their ordering, and covers pricing, access preconditions, and failure modes. Nothing an agent needs to call this 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% for the single `cvr` parameter, so the baseline is 3, but the description adds real value by prescribing how to obtain the CVR (search_companies first) and by constraining the tool to exactly one company.

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 (beneficial owners / UBO of one Danish company) plus the source register, and explicitly distinguishes itself from get_ownership and get_ultimate_owners. The listed return fields (name, person/company, share percent, conditions, country, period, ordering) make the scope unmistakable.

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 explicit routing rules: use search_companies when you only have a name, use get_ownership/get_ultimate_owners when there is no contract, and use one get_company call with `sections` when several sections are needed. It also tells the agent what to do on refusal rather than implying absence of data.

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