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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds meaningful behavioral context: multi-year history (2010-2026), record counts, HHI index, holder types, YoY changes, and substantial-holder voting percentages. It also explains historical-data usage via year/all parameters.

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?

The description is compact, front-loaded with the core purpose, and uses three sentences to cover resource, data scope, output dimensions, and usage hint. Every sentence adds value; the statistics are extra but not distracting.

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 an output schema present and annotations covering safety, the description is mostly sufficient. It explains data scope, history, and metrics, but the unsupported 'all=true' parameter creates a correctness gap. The overlap with get_substantial_holders is also not resolved, which could lead an agent to select the wrong tool.

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%, so the schema already documents ticker and year. The description adds a useful year example, but it also introduces '?all=true', a parameter that is absent from the input schema while additionalProperties is false. This is misleading: an agent following the description may try to pass an unsupported 'all' argument.

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 clearly states a specific verb and resource: 'Get top 20 shareholders and substantial holders (5%+) for an NZX company.' It also adds useful specificity about HHI, holder types, and YoY changes. However, it does not distinguish this tool from the sibling get_substantial_holders, which overlaps by name and by the substantial-holders portion of the description.

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 intended usage is implied by the first sentence, and the description gives invocation examples like 'Use ?year=2025 or ?all=true'. However, there is no explicit guidance about when to choose this tool over alternatives—particularly get_substantial_holders—and no exclusions or when-not-to-use guidance.

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