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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, non-destructive, closed-world), so the bar is lower. The description adds some behavioral context — waste is deducted, the result mirrors the site's Solve Backwards page — but says nothing about response shape or how conflicting page/query inputs are resolved.

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-loaded with the core purpose, but the middle clause ('the size of slab, room, deck or wall that is, as the site's Solve Backwards page works it, waste taken off') is grammatically tangled and forces re-reading. The single sentence is short but not cleanly structured.

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 an output schema present and full schema description coverage, the description need not explain return values. Adding the waste-deduction behavior and the non-sizing boundary makes it largely sufficient; only the sibling-routing gap leaves anything an agent might misjudge.

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% with 6 params, so the schema already documents 'have', 'page', 'query', 'detail', 'system', and 'settings' in detail. The description's '40 bags of concrete / 24 gallons of paint' examples echo the schema's own examples without adding format or unit syntax beyond them, so baseline 3 is appropriate.

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 inverse-calculation purpose with concrete examples ('40 bags of concrete', '24 gallons of paint') and names the output (area covered, size of slab/room/deck/wall). It partially differentiates from siblings via the scope boundary 'It does not size structure', but never names the forward-looking alternative like 'calculate'.

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 exclusion 'It does not size structure' implies when not to use it, and the material examples imply when it applies. However, there is no explicit routing guidance against the many sibling estimators (calculate, estimate_house, plan_room, plan_project), so the agent must infer the selection.

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