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

Annotations cover the safety profile (readOnlyHint, idempotent, openWorld, non-destructive). The description adds genuinely useful operational context: quota-charged register reads vs free cached results, register access limited to GB and AU, and that it PREPARES but can never submit an application. With annotations already carrying safety, this is solid added context, though exact quota costs and cache expiry semantics remain unspecified.

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-loads the core answer and the return-shape hint ('Returns nextAction first') and the never-submits constraint is prominent. It is information-dense but runs long with several parenthetical asides, slightly hurting scanability.

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?

No output schema exists, so the description correctly compensates by naming the primary return field ('nextAction first'). Combined with input-mode, cost, and jurisdiction caveats, an agent has everything needed 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 coverage is 100%, so the baseline would be 3, but the description adds real semantic guidance beyond the schema: the companyNumber-vs-dates tradeoff (register read costs a quota unit, supplying dates is free) and the instruction not to guess alreadyExtended. It adds meaning rather than restating field names.

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: whether a company can still apply for a filing extension, days remaining, and the cost of missing the window. It is clearly distinguishable from siblings like check_accounts and late_filing_penalty, and it explicitly says what it does not do (does not file accounts).

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 explicit when-to-use context ('the most useful thing to tell somebody who has just found a deadline'), the alternative path (the registrar's own service, which the tool links to), and the two input modes with their cost tradeoffs. It also states the hard rule that application must happen BEFORE the deadline it extends.

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