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

With no annotations, the description carries the full disclosure burden. It does add real behavioral context that structured fields lack — the base-rate-plus-8% calculation basis and a 1-credit cost — but it says nothing about the tiered fixed compensation amounts, the treatment of a missing paidDate, or the shape of the result, and there is no output schema to fall back on.

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?

Two compact clauses with zero waste; the domain and the formula are front-loaded, and the cost note is placed last where it belongs. It is lean to the point of being sparse, which is penalized under completeness rather than here.

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?

For a four-parameter financial calculation with no annotations and no output schema, the description leaves key questions unanswered: whether paidDate is optional and what that implies, which jurisdiction/statute applies, and what the response contains. The formula and cost are the only completeness wins.

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 baseline is 3. The parenthetical '(base rate plus 8%)' indirectly explains what baseRateOverride replaces (the statutory base rate), which is a small genuine addition, but dueDate, paidDate and invoiceAmount semantics come entirely from the schema.

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?

Names the specific resource and computation (statutory interest plus fixed compensation on a late commercial invoice) and even states the formula, so an agent can distinguish it from generic siblings like calculate, statutory_sick_pay or redundancy_pay. It stops short of naming an alternative tool or an explicit verb, but the domain is unmistakable.

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?

There is no when-to-use or when-not-to-use guidance and no prerequisites: it never says this applies to UK commercial (B2B) invoices, nor what happens if paidDate is omitted (accrual to today). The agent must infer the applicability from the title alone.

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