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

No annotations are provided, so the description carries the full behavioral burden. It usefully discloses the returned field set and the cost model ('Flat 5 points per successful run'), but says nothing about authentication, rate limits, or behavior when a registration number matches nothing.

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?

A single front-loaded sentence leads with the action and resource, then appends the cost note, which is genuinely useful to an agent managing a budget. No filler or repetition.

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 well by enumerating the returned fields and the cost. It only omits edge-case behavior (not-found, ambiguous identifiers), a minor gap for a tool this simple.

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 single parameter already documents both the accepted identifier forms and an example. The description restates 'registration number or registry URL' without adding format, validation, or normalization detail beyond the schema, so the baseline of 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?

The description states a specific verb (Get), a precisely scoped resource (one company from the New Zealand Companies Register), the accepted identifiers, and the returned fields. 'One company' scopes it against the list-style sibling run_nz_companies_search without the agent needing to open either schema.

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?

It tells the agent the accepted lookup keys (registration number or registry URL), which implies this is the single-record lookup tool, but it never states when to choose it over run_nz_companies_search or run_nz_company_documents. Usage is inferable rather than explicit.

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