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

Beyond the readOnlyHint annotation, the description discloses fact-freshness handling and the 15-day registration deadline, and reveals the verdict outputs ('ok / check / act_now'). This adds meaningful behavioral context without contradicting the annotation.

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 description is a single, information-dense sentence that front-loads the action ('Checks whether') and includes legal references, examples, and output verdicts. Every phrase adds value, though the density could be slightly off-putting.

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 no output schema, the description supplies the verdict values and mentions deadline/freshness handling, giving a solid picture of the tool's behavior. It does not detail all possible return fields, but for a check tool the verdict is the primary output and the schema covers inputs well.

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 high (86%), so the baseline is 3. The description adds contextual examples (Google Ads, Meta, ChatGPT, hosting) that map to foreignServicePurchase and foreignSales, but it does not explain individual parameters beyond what the schema already provides.

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?

The description clearly states the tool's function: checking whether foreign service purchases or sales to EU businesses trigger identifikovaná osoba status under specific legal sections (§ 6h/§ 6i ZDPH), with a definitive verdict output. It distinguishes from sibling tools like check_thresholds by focusing on the IO trigger rather than general VAT thresholds.

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?

The description provides clear context for when the tool is relevant (buying foreign services, selling to EU businesses) with concrete examples, and mentions the 15-day deadline. However, it does not explicitly name alternative tools or state when not to use this tool, leaving some room for the agent to infer applicability.

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