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

Annotations already declare readOnlyHint/openWorldHint/destructiveHint=false, and the description adds value beyond them: the 2-credit cost, that bands are ranges rather than exact figures, and the tier_restricted refusal behavior at no cost with instructions not to report missing data as absent. That last point is a genuine failure-mode disclosure no annotation carries.

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 the output shape, then routes to alternatives, then the cost and failure mode. It is dense but every clause carries operational information; there is no filler or restatement of the tool name.

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?

With one parameter, no output schema, and safety already covered by annotations, the description still explains return contents, scope limits (first link only), cost, and the tier_restricted outcome. 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% and the single `cvr` parameter is fully documented with a pattern, so the schema carries the type contract. The description adds lookup context — the CVR is the key, and search_companies should be used first when only a name exists — which is modest but real added meaning beyond the schema.

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 ('direct legal owners of one Danish company from the public ownership register') and enumerates what each record contains: ownership/voting bands, person-vs-company flag, and CVR. It explicitly distinguishes itself from get_ultimate_owners and get_real_owners, so an agent can route without opening schemas.

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 alternatives with conditions: get_ultimate_owners to follow holding chains, get_real_owners for UBO, search_companies when only a name is known, and get_company with `sections` when the profile or multiple sections are needed. It also states the cost trade-off, which is exactly the kind of when-to-use guidance that selects between siblings.

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