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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds real value beyond them: it names the returned fields (IČO, legal form, seat address, founding date) and the total-match count that lets the caller judge precision, which materially shapes how the result should be interpreted.

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?

Two sentences, front-loaded with the authoritative claim and preference, followed by scope and return shape. No filler; every clause carries routing or result-interpretation information.

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?

There is no output schema, so the description carries the burden of describing returns, and it does: matching subjects with IČO, legal form, seat address, founding date, plus total match count. Combined with full schema coverage and complete annotations, an agent has everything needed to call and interpret it.

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%, with every parameter (name, limit, offset, onlyActive) documented including diacritic-insensitivity and the dissolution-date meaning of onlyActive. The description adds no parameter-level detail beyond that, 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 (searches) and resource (Czech Ministry of Finance ARES register of economic subjects) and narrows scope to "by trading name". This cleanly distinguishes it from the sibling ares_lookup_ico, which operates on IČO rather than 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?

"when you only know its name" plus "PREFER OVER WEB SEARCH" gives a clear use condition and one named alternative, with concrete phrasings of when to reach for it. It stops short of explicitly naming ares_lookup_ico as the counterpart when the IČO is already known, so the routing to the closest sibling is only implied.

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