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

Annotations already declare readOnlyHint, idempotentHint and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context: that omitted parameters silently fall back to defaults, that those defaults are echoed in the response, and that the math mirrors a named external calculator (torgix.ai/learn), which helps an agent trust and explain the output. It stops short of describing the response shape beyond 'lists the defaults'.

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 sentences, zero filler. The cost-component list comes first to establish what is computed, followed by the input contract in the same breath. 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?

For a 13-parameter, all-optional-but-two calculation tool with no output schema, the description covers the two things an agent cannot get from structured fields: the defaulting contract and where the defaults come from. A brief note on what the result object contains (per-hour total plus breakdown) would close the last gap.

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%, so every one of the 13 parameters already has a documented meaning and default in the schema. The description only restates the required/optional split and the defaulting behavior, adding no per-parameter meaning the schema lacks. Baseline 3 applies when the schema carries the weight.

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 ('Calculates') and a precisely scoped resource ('what a machine really costs per hour to own and operate'), then enumerates the cost components covered (depreciation, cost of capital, insurance/taxes/storage, fuel, lubricants, repairs, wear parts). No sibling tool touches cost math, so the agent can route here without ambiguity.

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?

Explicitly names the two required inputs ('Purchase price and hours per year are required') and states what happens to everything else ('anything else left out uses the calculator's defaults, which the answer lists'). This is clear operational guidance for how to call it, though it offers no when-to-use versus alternatives guidance for the broader fleet decision family (e.g., repair_rebuild_or_replace).

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