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

Annotations already cover read-only, idempotent, non-destructive and closed-world behavior, so the bar is lower; the description still adds that it is 'pure arithmetic, no network or model' and discloses what is not priced and what dated sources back the ranges.

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?

Four compact sentences, front-loaded with the core estimate purpose and then the scoping caveats. Dense but each clause carries information, though 'Includes unpriced checks' is vague relative to its neighbours.

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?

No output schema exists, and the description compensates by describing the return as national installed ranges with no typical figure plus two reference cards and dated sources. Slightly imprecise about result structure, but sufficient to call the tool correctly.

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%, so surface, existing and sections are already fully documented, and the description largely restates them ('for a given size', removal only for existing concrete). Baseline 3 is appropriate where the schema does the heavy lifting.

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 ('Estimate driveway replacement costs') scoped by size, and distinguishes itself from surface-adjacent siblings (concrete_calculator, flooring_cost, fence_cost) by naming the ten surfaces it compares in one call.

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 clear context: one call compares all ten surfaces, and it explicitly scopes out base, drainage and permits, and limits removal pricing to existing concrete. It stops short of naming a sibling alternative to use instead, but the exclusions make the right call obvious.

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