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

Annotations already cover read-only, idempotent and open-world behavior, so the description focuses on what the call yields: a 'unified record' with status, address, legal form, activities, plus source and retrieved_at. The mention of a 'unified' record and provenance fields adds real context about how data is aggregated, which annotations do not convey.

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: the action first, then the return shape. No filler or repetition of the title, though the returned-fields list is dense and could be trimmed if an output schema existed.

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 carries the burden of describing the return value and does so by naming the record's key fields and provenance metadata. For a two-parameter lookup tool this is close to complete; only error/not-found behavior is unaddressed.

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% and the schema already spells out the country enum (SK = RPO, CZ = ARES) and ID constraints. The description only restates that the ID belongs to the register of the given country, adding no syntax or format detail beyond the schema. 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?

Uses a precise verb+resource ('Fetch one company ... by its ID') and scopes it to 'the official register of the given country', which implicitly separates it from the sibling search_company. It stops short of naming the sibling, so differentiation is inferred rather than stated.

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 'one company ... by its ID' framing implies this is the direct-lookup path versus a search, but the description never states when to prefer it over search_company or what to do if only a name is known. Usage is implied, not specified.

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