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

With no annotations, the description carries the full burden; it usefully discloses the exact data returned and a cost signal ('5 point per returned record'), which goes beyond the schema. It does not cover auth requirements, rate limits, or not-found/error behavior.

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?

Purpose and input forms are front-loaded, followed by the returned-field list and the pricing note. The field enumeration is long but each item is informative; no filler sentences.

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 and no annotations, the description compensates by listing the fields returned and the accepted identifier forms, which is close to sufficient for a single-record lookup. Missing only edge-case behavior (invalid org number, missing record).

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 single parameter already documents both accepted forms plus an example (923609016). The description restates 'organisation number or registry URL' without adding format, normalization, or URL-handling detail beyond the schema.

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 and resource ('Get one company from the Norway registry (Brønnøysundregistrene, Enhetsregisteret)') and enumerates the returned data. The singular, identifier-driven scope implicitly separates it from run_no_companies_search, though no sibling is named explicitly, which keeps it from a 5.

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?

Usage is only implied: the agent can infer this is for looking up a single known company by org number or URL rather than searching. There is no explicit when-to-use, no exclusion, and no pointer to run_no_companies_search for the find-by-name case.

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