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

Goes well beyond the readOnly/openWorld annotations by disclosing the paid model ($0.002 USDC per successful call via x402 on Base/Solana/Arc) and that failed calls are not charged — critical cost behavior an agent must know before calling. It also states the licensing (CC BY 4.0) but omits any rate limits or latency/auth requirements beyond the payment rail.

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 tight sentences, front-loaded with the verb+resource, then the negative constraint, then cost/licensing. Every sentence carries distinct, actionable information with no padding.

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 already present, the description covers everything an agent needs: what it returns, the identifier format, the unsupported search mode, and the billing model. Nothing material 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 description coverage is 100%, so the 'ico' parameter is already documented as an 8-digit Slovak company ID. The description only restates that format without adding validation rules, edge cases, or lookup fallbacks, 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?

States a specific verb and resource ('looks up a legal entity by its 8-digit company ID (IČO)') and enumerates the return payload (names, establishment date, registry court, address). Combined with the Slovakia RPO register scoping, an agent can immediately distinguish it from the many other country-registry siblings.

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?

Explicitly rules out name-based search ('Search by name is not supported by the API'), which is the most likely wrong invocation for a company register tool. It does not, however, name or point to any alternative sibling (e.g., other national registers), so routing among siblings is left to inference.

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