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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that: PSC data mirrors the public register and is not independent verification of beneficial ownership, plus the paid x402/USDC access model on Base mainnet — a real operational constraint an agent must know before invoking.

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?

Four short sentences, front-loaded with the verb and resource, followed by use case, a data-provenance caveat and the price. Each sentence carries information, though the pricing sentence is somewhat boilerplate-adjacent and could be tightened.

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, return values need no explanation, and the single required parameter is fully documented in the schema. The description covers provenance and payment prerequisites, leaving only minor gaps such as behavior when a company has no recorded PSC.

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 a single parameter at 100% schema description coverage, with the pattern and an example already documented in the schema. The description contributes nothing further about company_number format or sourcing, so 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?

The description names a specific verb and resource — 'Retrieve Persons with Significant Control (PSC) recorded for a UK company at Companies House' — and enumerates what comes back (nature of control, identity information). It is clearly separable from sibling data tools by the PSC domain term, though it never explicitly contrasts itself with get_company_officers or get_entity_owners, which an agent must infer from domain knowledge.

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?

'Useful for company ownership research and KYB-supporting due diligence' gives a use context but not a selection rule: it doesn't say when to prefer this over get_company_officers (officers/directors) or get_entity_owners (non-UK entities), nor when not to call it. Usage is implied rather than prescribed.

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