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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description adds valuable behavioral context beyond that: it flags overseas corporate PSC entries as a beneficial-ownership risk signal and explains the special explanatory note for widely-held PLCs with no registrable PSC.

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 short, direct, and front-loaded with the core action and resource. Every sentence contributes useful information about what is returned, a risk flag, or a meaningful edge case.

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 single-parameter read-only tool with an output schema and helpful annotations, the description covers the main content, a special risk behavior, and an unusual empty-result case. Nothing important is missing for an agent to select and invoke the tool correctly.

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?

There is only one parameter, company_number, and the input schema already describes it fully with length constraints, format, and an example. The description adds no parameter-level detail, which is acceptable given 100% schema coverage, so the baseline score 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 opens with a specific verb and resource: 'Fetch Persons with Significant Control (beneficial ownership) for a company.' It also names the key data returned, distinguishing it from related company tools like dd_company_officers and dd_company_profile.

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 resource and terminology make the use case clear, but there is no explicit guidance about when to prefer this tool versus alternatives such as dd_company_officers or dd_company_profile. The distinction is implied strongly by 'beneficial ownership' rather than stated directly.

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