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

Annotations already declare readOnlyHint and openWorldHint, but the description adds genuinely useful context beyond them: a $0.002 per-successful-call price, the x402 payment rails (Base, Solana, Arc), and that failed calls are not charged. It doesn't mention rate limits or latency, but the cost/charging model is exactly the kind of behavioral detail annotations can't convey.

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-loaded with the data source and identifier, followed by the field list, the anonymisation caveat, and pricing. Dense but every clause adds information; only slight redundancy between the description and the schema on the 8-digit requirement.

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?

For a single-parameter lookup with an output schema and read-only annotations, the description covers the data source, returned fields, data limitations, and cost model — everything the agent needs to decide to call it and how the call is billed.

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?

The single parameter has 100% schema description coverage including an example (33302047), and the description only restates that it must be an 8-digit KVK number. Baseline 3 is appropriate since the schema already carries the semantics.

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?

Names the exact resource (Dutch company data from the KVK open High Value Dataset) and enumerates the returned fields: active status, start date, legal form, postcode region, SBI codes. An agent can immediately tell this apart from sibling registry tools like france_annuaire_entreprises by country and dataset source.

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?

Clearly scopes usage by stating the open set is anonymised and that names and addresses are not included, which tells the agent this tool cannot answer identity/address questions. However, it never explicitly names an alternative source for full company records or states when not to use it.

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