list_persons_with_significant_control

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=true, so the safety profile is covered. The description adds important behavioral context beyond the annotations: an empty list can mean the company filed a no-PSC statement, which this tool does not read, and corporate owners are returned with a registration number. This prevents a common misinterpretation of an empty result.

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 front-loaded with the core definition and then delivers two high-value behavioral facts: the upward-chain follow-up via get_company_profile and the empty-list caveat. Every sentence earns its place, with no repetitive or filler content.

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?

Given the rich schema, read-only annotations, and an output schema, the description covers everything an agent needs to invoke it correctly: what it returns, an important empty-result interpretation, and how to continue a corporate-ownership investigation. No critical operational detail is missing.

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%, so the input schema already documents all four parameters clearly, including defaults, bounds, and the 'next_start_index' paging hint. The description adds no extra parameter-level meaning beyond what the schema provides, so the baseline of 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?

The description opens with the specific verb 'List' and the precise resource 'who owns or controls a company (its persons with significant control)', then defines the scope with concrete thresholds (over 25% of shares or votes, right to appoint the board). This clearly distinguishes it from sibling tools like list_officers and list_filings by focusing on ownership and control rather than directors, filings, or charges.

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 description gives a clear context for use: when the agent needs to know who owns or controls a company. It also provides a concrete routing hint, telling the agent to pass a UK corporate owner's registration number to get_company_profile to trace ownership upward. It does not explicitly state when not to use this tool versus list_officers, but the ownership-focused definition makes the intended use clear.

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