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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), but the description adds non-obvious behavioral context: the call costs $0.005 USDC per call via x402, which an agent needs before invoking. It also enumerates the returned fields, which is more than the annotations provide.

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?

Front-loaded with the core action, followed by the returned fields and then the cost. Two sentences with minimal waste, though the field enumeration is dense inline rather than structured.

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 no output schema, the description carries the burden of describing returns, and it does so by listing company, status, role, and appointed/resigned dates, plus the matching criteria (birth month/year) and cost. Complete enough for an agent to call it 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?

Schema description coverage is 100%, so both parameters are already documented in the schema. The description clarifies the two-phase relationship between 'name' (match) and 'pick' (expand a match), but adds little syntax or format detail beyond what the schema states.

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 states a specific verb and resource: look up a person in the UK company register and enumerate their directorships and secretary roles. It distinguishes itself from company-level siblings (uk_company, uk_companies_search) by scoping to a person, though it never names the alternatives explicitly.

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?

Usage is implied through the described two-stage flow: match officers by name, then expand the chosen match via pick. There is no explicit when-to-use versus alternatives guidance, no exclusions, and no note on what to do if no match is found.

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