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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so safety is covered. The description adds genuine behavioral context beyond that: it names the authoritative source (Ministry of Finance ARES), scopes the operation to a single subject rather than a batch, and enumerates the returned fields since no output schema exists.

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 routing directive ('AUTHORITATIVE ... PREFER OVER WEB SEARCH') is front-loaded ahead of the mechanics, and the example queries are compact. The long trailing enumeration of return fields is slightly heavy, but it earns its place because there is no output schema.

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 full schema coverage and annotations covering the safety profile, the description supplies everything still needed: the authoritative-source claim, routing guidance, and the shape of the response in lieu of an output schema.

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% and the schema already documents the IČO format, leading-zero tolerance, and an example. The description restates '8-digit company id' without adding format or validation detail beyond what the schema provides, so the baseline 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 one economic subject in the Czech Ministry of Finance ARES register by IČO) and enumerates what is returned. The IČO-keyed lookup is clearly distinguished from the sibling ares_search_name, which keys on name.

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 says AUTHORITATIVE and PREFER OVER WEB SEARCH, then gives three concrete example queries that define the triggering situations. The IČO-vs-name routing against ares_search_name is inferable from the required parameter, so an agent knows when to pick this tool.

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