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

Annotations already establish readOnly=true, idempotent=true, destructive=false and closed-world, so the safety profile is fully covered. The description adds a genuine behavioral trait beyond them: the tool rounds to 'whole containers', telling the agent the output is a discrete container count rather than a raw fractional volume.

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?

A single front-loaded sentence naming the computation first, then the inputs. No filler, no redundant restatement of the title, and every clause maps to actual tool behavior.

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?

An output schema exists, so return values need no explanation, and the high schema coverage handles parameter detail. The only shortfall is the thin usage guidance around choosing area vs surfaces, but the oneOf in the schema largely compensates for that.

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 88%, so the schema already documents area, coats, coverage, openings, containerVolume and units in detail. The description only restates the parameter concepts (openings, whole coats, per-coat coverage) without adding syntax, defaults, or interaction rules beyond what the schema provides. Baseline 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 (Calculate) and resource (paint volume and whole containers) plus the input modes it accepts (entered area or supported surface geometry). No sibling tool competes in this space (concrete/mulch/gravel/volume calculators are distinct materials), so the resource is unambiguously identified.

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 phrase 'from entered area or supported surface geometry' implicitly signals the two mutually exclusive input paths, matching the schema's oneOf. However, there is no explicit when-to-use/when-not guidance, no prerequisites, and no named alternative, so usage is only implied rather than stated.

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