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

Annotations already establish readOnly/idempotent/non-destructive, and the description adds genuinely new information beyond them: the returned units and the scope boundary (turnover flow included, equipment sizing excluded). For a stateless calculator no further behavioral disclosure (auth, rate limits) is really needed.

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 dense sentences with zero filler; the core purpose and units come first, the scope limitation second. Every clause earns its place.

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 eight parameters, no output schema, and zero schema description coverage, the definition is under-specified for an agent to invoke correctly across all paths. It never explains the shape-to-dimension mapping or the turnoverHours input, both of which the agent must infer from the schema alone.

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 0%, so the description must carry the load, and it only partially does. It clarifies the unit parameter (feet or meters) and implies the shape/dimension families, but leaves the 'quick' surface-area mode, which dimensions pair with which shape (width/length vs diameter vs surfaceArea), and the turnoverHours parameter and its default unexplained.

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?

Specific verb ('Estimate') plus resource ('swimming pool volume') and explicit output units (US gallons and liters). It also enumerates the geometry families it handles (rectangular, round, oval, surface-area), which cleanly distinguishes it from the sibling calculate_pool_salt.

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?

Gives a clear scope boundary: 'Includes turnover flow, not equipment sizing,' which tells the agent when this tool is the wrong pick. It stops short of naming an alternative tool for the excluded case, so it is context rather than full routing guidance.

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