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

With no annotations, the description carries the full burden. It helpfully enumerates the returned attributes and discloses a pricing trait ('Flat 5 points per successful run'), which is real behavioral value. It stops short of stating auth requirements, failure behavior for unknown IDs, or rate limits.

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 tight sentences, with the primary purpose front-loaded before the field list and the cost note. The returned-field enumeration is long but earns its place given there is no output schema; nothing is redundant.

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 one-parameter lookup with no output schema and no annotations, the description compensates by listing the return fields and the cost, which is what an agent needs to judge value. Only minor gaps remain: no error/not-found behavior and no explicit routing to the search sibling.

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 parameter already documents 'Business ID (Y-tunnus) or registry URL. e.g. 0112038-9'. The description restates the same accepted formats without adding syntax, validation, or normalization detail, so the baseline 3 is appropriate.

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?

Specific verb ('Get one company') plus resource and registry ('Finland registry (PRH / YTJ)'), and the acceptance keys (Business ID / registry URL) are stated. The singular 'one company' cleanly separates it from the sibling run_fi_companies_search bulk/name lookup.

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 phrase 'Get one company ... by Business ID or registry URL' implies the lookup use case and, by contrast with run_fi_companies_search, the single-record scenario. However, no alternative is named and no when-not guidance or prerequisites are given, so the agent must infer the routing.

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