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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds genuine behavioral context: that the register is auto-compiled and cross-references all four NZXplorer platforms, indicating an aggregated derived view rather than raw filings.

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?

Three sentences, front-loaded with the verb and resource before the detail list and usage triggers. The data-source enumeration is long but each item is informative rather than filler.

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?

An output schema exists, so return values need not be explained, and the description covers what is produced, its provenance, and when to reach for it. Minor residual gap is the absence of routing guidance against the many adjacent director tools.

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 'ticker' parameter is documented with a format example (e.g. FPH). The description adds no parameter semantics beyond that, so the 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?

Specific verb ('Get') plus a precisely named resource ('Companies Act s189 interest register for an NZX company'), followed by an enumeration of what it compiles. An agent can distinguish this legal-register view from siblings like get_director_conflicts or get_company_directorships without opening any 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?

The final sentence gives clear triggering contexts: director interests, conflicts of interest, related party positions, board independence. It stops short of naming alternatives or when-not-to-use, which matters given the dense cluster of overlapping director/conflict tools.

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