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

With no annotations, the description carries the full behavioral burden; it usefully discloses the data source and the cost ($0.25 USDC), which is real context beyond structured fields. However, it does not state that the operation is a read-only lookup, what happens on no-match or multiple matches, or the response envelope shape. For a paid external lookup with zero annotation coverage, this is adequate but incomplete.

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?

Three short, front-loaded sentences: purpose, returned fields, then search keys with an example. The field enumeration is dense but informative; only the price token feels tacked on rather than integrated.

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?

The description compensates partly for the missing output schema by listing returned data fields, and it discloses the source and price. Given six undocumented parameters, no annotations, and no output schema, the gaps around ambiguous parameters (q, vat, number, limit) and failure behavior leave it short of complete.

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 0% across 6 parameters, so the description must compensate. It covers only two of them, clarifying that 'cvr' is 8 digits and that name lookup is supported; 'q', 'vat', 'limit', and 'number' are left completely unexplained, including how 'q' differs from 'name' and how 'vat' differs from 'cvr'.

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 gives a specific verb-plus-resource ('Danish company lookup via CVR') and names the underlying registry (apicvr.dk / Erhvervsstyrelsen), which cleanly separates it from sibling country lookups such as uk_company, no_company, and fr_company. It also enumerates the fields returned (status, address, direktion/ejere, red flags). Differentiation from aggregation-style siblings like company_full or kyb_report is only implicit.

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 states the supported lookup keys ('Search by cvr (8 digits) or name') and gives a concrete example, so basic invocation context is implied. There is no when-to-use versus when-not guidance and no mention of alternatives such as company_full or registry_batch for this data, leaving selection up to inference.

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