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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds 'latest-known,' which usefully signals a snapshot rather than real-time or historical data. It says nothing about empty results, unknown company handling, or result shape.

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?

A single front-loaded sentence with zero waste. For a simple two-parameter lookup tool, this is appropriately sized and immediately readable.

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 annotations covering safety, a fully described two-parameter schema, and no output schema, the description is minimally adequate. However, with no output schema present, the description could have said what a shareholder record contains (identity, stake, voting rights) and how 'latest-known' dates are conveyed.

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%, so company_number format and locale options are fully documented in the schema. The description adds nothing about parameters, though 'latest-known' implicitly signals there is no as-of/date parameter for historical queries — a small but real clarification.

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 (Get) and resource (shareholders of a company) with the qualifier 'latest-known' indicating data currency. It is distinguishable from get_employees, get_financials, and get_mandates by resource, but it never explicitly contrasts with the adjacent get_participations or get_held_mandates, which cover related ownership concepts.

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 gives no when-to-use context and names no alternatives. An agent gets no rule for choosing this over get_participations or get_mandates, even though those overlap conceptually with shareholder data. Usage is only inferable from the resource name.

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