preview_overage_charge

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

With no annotations, the description carries the full burden. It does disclose a meaningful behavior — extra-printer charges are free on every plan, so the previewed amount is effectively zero — but does not state that the call is read-only, has no side effects, or what the returned value looks like. Partial disclosure nets a 3.

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 short sentences, no filler, and the core purpose is front-loaded before the 'Free on every plan' note. Slightly terse rather than padded, so it earns its length.

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 single-parameter, no-output-schema preview tool this is close to adequate, but with no annotations and no return-value information the agent cannot tell what the response contains (currency, breakdown) or confirm it is a safe read. The 'free on every plan' line is also ambiguous about whether the tool is useful at all.

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?

There is one parameter (active_printer_count) with 0% schema description coverage, so the description must compensate. 'A number of printers' loosely maps to the parameter but adds no unit, range, or semantics (e.g., whether it counts currently active vs. proposed printers) beyond the schema title.

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?

The description states a specific computed quantity — the extra-printer cost for a given number of printers on the caller's plan — which is enough to distinguish it from generic cost tools like estimate_cost. It never names a verb (preview/estimate) and gives no sibling differentiation, so it stops short of a 5.

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 statement of when to use this over the many other cost-estimation siblings (estimate_cost, project_cost_summary, print_cost_intelligence), and no prerequisites or exclusions. The only usage hint is implicit in 'would cost'.

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