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

Annotations already cover read-only, idempotent, open-world, and non-destructive behavior, but the description adds substantial context beyond them: the meaning of 'pending' versus 'overdue' (with an explicit warning not to report pending as a failure), the 18 November 2026 enforcement date, the 24-hour cache, and the Pro-plan requirement. This is rich behavioral and interpretive detail.

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?

The description is front-loaded with the core purpose, then adds return fields, a critical interpretation warning, and prerequisites. Every sentence carries actionable information, and the IMPORTANT warning is placed prominently rather than buried.

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 compensates by naming the returned counts (directors_total, directors_verified, directors_pending, directors_overdue) and the per-person unverified_persons structure. Combined with status semantics and caching, an agent has everything needed to call and interpret the tool 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 the single parameter's format and zero-padding rule are already documented in the schema. The description adds no further parameter-level syntax or constraints, so the baseline of 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?

States a specific verb and resource: 'Check a UK company's ECCTA identity-verification status,' then enumerates exactly what is returned (who verified, pending, overdue). This is clearly distinguishable from siblings like get_directors or get_psc, which deal with officer/PSC listings rather than compliance status.

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?

Provides prerequisites ('Requires a Pro plan or above') and a caching caveat ('Cached for 24 hours'), which help an agent decide whether it can call the tool. However, it never explicitly says when to use this tool versus alternatives such as get_directors or get_psc, leaving usage largely implied by the purpose.

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