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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered without description help. The description adds useful behavior by naming the return shape (area_m2, volume_m3, weight_kg, bags_25kg), which hints at the underlying material assumptions, but says nothing about waste factors, defaults applied, or edge cases.

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: the action and its scoping inputs come first, the return shape second, with zero filler. Every clause carries information an agent can act on.

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?

Because an output schema exists, the description need not spell out return values, yet it does so briefly and consistently. For a two-parameter read-only calculator the coverage is sufficient; only the absence of any plaster-type/mix assumption or waste-factor note keeps it from being fully complete.

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%: area_m2 and thickness_mm are both documented in the schema, including the default of 13mm. The description names 'surface' and 'thickness' but adds no unit conventions or constraint detail beyond what the schema already states, 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 ('Calculate plaster volume and weight') plus the two inputs that drive it (surface, thickness), which clearly separates it from generic calculators like calculate_volume or calculate_area. It stops short of distinguishing itself from the adjacent construction siblings (calculate_brick_count, calculate_concrete_mix, calculate_tile_quantity), pointing only at list_bundles rather than naming a real alternative.

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?

Usage is implied by the domain ('plaster ... given surface and thickness'), and the pointer to list_bundles for other 'construction' calculators gives a browsing affordance. However there is no explicit when-to-use/when-not-to-use guidance and no routing against the many overlapping construction-material calculators in the sibling list.

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