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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds value beyond them by disclosing the data source (Companies House), the historical scope ('or has held'), and the credit cost of one per call, which the agent needs for budget decisions. It omits any note on result volume or pagination for prolific directors.

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?

Three tight sentences, front-loaded with the resource definition, then the use case, then the invocation and cost. Every sentence carries information the agent needs; nothing is redundant with the schema or annotations.

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 still conveys the shape of the result (every company a person is tied to) and the cost, which is adequate for a two-parameter lookup. Minor gaps remain around pagination, result limits, and whether partial name matches are supported, but nothing essential to a correct call 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 coverage is 100% with two self-documented optional string parameters, so the baseline is 3. The sentence 'Pass a name or an officerId' usefully confirms that either one suffices rather than both being required, but adds no detail on name format (fuzzy vs exact match) or what happens if both are supplied.

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?

States a specific verb and resource: retrieving all directorships a person holds or has held across UK Companies House records, with the reverse-lookup framing 'Find every company a director is tied to.' This is clearly distinct from company_officers in practice, but the description never names that sibling or explicitly contrasts the two directions of lookup.

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?

Gives a use context ('due diligence and conflict checks') and tells the caller to pass a name or an officerId, which is genuine usage guidance. However, it never says when to prefer the name path over the officerId path, or when to use company_officers / disqualified_officers instead, leaving alternative selection to inference.

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