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

Annotations only declare readOnlyHint and openWorldHint; the description adds substantial context the annotations lack: the upstream data source (Mercantile Registry gazette BORME), the pricing model ($0.002 USDC per successful call via x402 across Base/Solana/Arc), and that failed calls are free. That billing disclosure is exactly the kind of pre-call behavior an agent needs; it does not, however, cover rate limits or latency.

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 paragraph that leads with what data you get, then how to invoke it, then the cost. The long field enumeration is dense but every item is a concrete field an agent may need when deciding to call, so nothing is wasted.

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?

With an output schema present, the description correctly does not re-explain return shapes, and it covers source, access modes, fallback, and payment terms. The remaining gap is minor: nothing about pagination/limits beyond the officers cap or what a failed lookup returns.

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 coverage is 100%, so the schema already documents q, slug and officers, making 3 the baseline. The description adds a little beyond it by explaining that a slug skips the search and that non-exact name matches are still listed, but it adds nothing about the officers range or default.

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 a specific resource (Spanish company dossier) and its source registry (Empresia/BORME), then enumerates the exact fields returned, which lets an agent tell it apart from the many other national business-registry siblings. It stops short of naming an explicit alternative or contrasting itself with the non-Spanish registries in the sibling list.

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?

"Search by company name or open a company by its Empresia slug; other matches are listed" explains the two invocation modes and the fallback behavior, which is genuine usage context. It gives no when-to-use vs. when-not guidance against alternatives (e.g., when to prefer a different registry or a people/company profile tool).

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