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

The annotations already establish that this is a read-only, idempotent, non-destructive calculation. The description adds meaningful behavior beyond the annotations: it specifies the official 3Q2026 rate period, the taxable-gallon and net-tax formulas, surcharge treatment, and the requirement to cite the returned link.

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?

The description is front-loaded with the purpose and then packs the necessary calculation rules into a compact paragraph. Every sentence contributes operational meaning, with no filler.

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 calculation tool with rich schema coverage and no output schema, the description is largely complete: it explains the rate period, formula, surcharges, and citation expectation. The main remaining gap is that it does not describe the returned per-jurisdiction fields or totals in any detail.

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 the schema already documents the parameters in detail. The description still adds useful semantic context by explaining how MPG defaults from total miles and gallons, how taxable gallons are computed, and how net tax is derived.

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?

The description states a specific verb and resource: estimating IFTA fuel tax owed or credited per jurisdiction for a quarter. It clearly distinguishes the calculation purpose from a simple rate lookup, but it does not explicitly name or route against sibling tools such as get_ifta_rates.

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?

It gives clear input guidance for using the tool, including miles, tax-paid gallons, and the optional MPG override. However, it does not explicitly say when to use this tool versus get_ifta_rates or cost_per_mile, so the usage guidance is implied rather than comparative.

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