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

Beyond the readOnly annotation, the description discloses the credit cost, the marketing-protection flag and its legal implication, and that empty fields are filled from the provider's own contact data where the plan covers it. These are meaningful behavioral traits an agent needs.

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?

The description is front-loaded with the returned fields, then adds usage and legal caveats. It is dense but every sentence carries useful information; minor tightening could improve flow.

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?

Because there is no output schema, the description appropriately explains what is returned, including the registered dates and the reklamebeskyttet flag. It also covers cost and sibling alternatives, making it complete for this tool.

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 a single required parameter and schema coverage is 100%, so the schema fully documents the CVR number format. The description reinforces lookup by CVR but adds no format or validation detail 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?

The description states a specific resource (phone, email, website and registered address for one Danish company) and its scope (one company, looked up by CVR). It distinguishes itself from siblings such as get_company explicitly.

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?

It gives explicit when-to-use alternatives: use search_companies first when only a name is known, and use get_company instead when the user wants more than contact details. Cost equivalence with get_company is also stated.

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