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

Annotations already declare readOnlyHint, idempotentHint and non-destructive behavior, so the safety profile is covered. The description adds that this is authoritative register data rather than a cache, but says nothing about failure behavior for an unknown CVR or data freshness — modest added value on top of the annotations.

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 naming the source register and then itemizing the payload. The field list is long but each item tells the agent what will be available; no filler or restated 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?

An output schema exists, so the enumerated return fields are largely redundant rather than compensating for a gap. What is genuinely missing is operational context — how to obtain a CVR when only a name is known, and what happens on an invalid or unknown identifier — for a tool that is otherwise simple.

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?

There is one parameter at 100% schema description coverage, and the schema already explains the 8-digit format, an example value, and DK-prefix tolerance. The description adds no additional meaning about the cvr argument, so the baseline of 3 applies.

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 resource (full company profile from the CVR register) and enumerates the fields returned, so an agent knows this is a single-company detail lookup rather than a search. It does not explicitly contrast itself with siblings such as search_companies or company_financials, relying on the title's 'by CVR' to convey the lookup key.

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?

There is no when-to-use guidance: nothing says this requires a known 8-digit CVR, nor that search_companies should be used first when only a name is available, nor that company_financials/company_people cover the related slices. Usage is only inferable from the title and the required cvr argument.

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