Get persons with significant control

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

With no annotations, the description carries the full burden, and it delivers. It discloses decoded control types, ECCTA verification fields, the precise meaning of pending vs unknown vs overdue, that corporate entities carry a company number and no verification fields, detection of PSC exemptions, and a 24-hour cache. This goes far beyond a simple 'returns PSC data' and gives the agent a clear model of tool behavior.

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?

Although the description is lengthy, every sentence serves a purpose: core function, return types, control-type decoding, verification status semantics, corporate vs individual differences, exemptions, and caching. It is front-loaded with the primary purpose and then layers detail in a logical order. No filler or redundancy.

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?

Without an output schema, the description must explain return values, and it does so thoroughly. It covers PSC categories, control types, verification status fields and their interpretations, corporate entity specifics, exemptions, and caching. For a complex tool returning varied entity types, this is sufficient for an agent to cal it correctly and interpret the results.

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?

The input schema already documents company_number with an example and zero-padding guidance, and schema description coverage is 100%. The description does not add any additional parameter-level meaning or nuance, so it stays at the baseline 3. It correctly focuses on output behavior rather than re-explaining the parameter.

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+resource: 'Get the PSC (Persons with Significant Control) register for a UK company.' It then enumerates exactly what is returned (individuals, corporate entities, legal persons) with ownership thresholds, which clearly distinguishes it from sibling tools like get_directors or get_company. The content is unambiguous and informative.

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 provides clear context on what the tool returns, but it never explicitly states when to use this tool vs alternatives such as get_psc_chain or get_company. No exclusion criteria or alternative routing is given. The usage scenario is implied by the specialization to PSC registers, but the agent is left to infer when this tool is the right choice.

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