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

Annotations already declare the safe read/idempotent profile, and the description adds genuinely new behavioral context: the subscription-tier gating and the indexing order. It does not mention result freshness windows or pagination behavior, but the plan restriction is exactly the kind of pre-call constraint the annotations cannot express.

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 compact sentences: the first front-loads what the resource is and its ordering, the second carries the conditional usage constraint. No filler, though 'the most recently indexed last' is slightly dense phrasing.

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 full schema coverage, no output schema and rich annotations, the description supplies the two things the structured data cannot: the plan gate and the alternative tool. An agent has enough to decide whether it can call this at all; only cross-sibling comparison with the search tools is left implicit.

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 every parameter including the intricate persoana_fizica caveat is already documented in the schema. The description only restates the filter dimensions (CAEN, county, natural persons) without adding syntax or defaults, which matches the baseline-3 case where the schema does the heavy lifting.

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 the specific resource (newly registered companies and sole traders in Romania), the ordering ('most recently indexed last') and the optional filters, which is far more than the title provides. It does not, however, distinguish itself from siblings like find_company or lookup_company, so the agent must infer that this is a recency list rather than a search tool.

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 explicitly states the plan prerequisite ('Only on the plans that include the list') and names the sibling that works universally ('count_new_companies works on every plan'), which is a real routing rule. It gives no guidance on when this list is preferable to find_company or lookup_company for a given company.

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