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

With no annotations, the description carries the behavioral disclosure burden. It adds useful caveats like '2025 base rates — local rates vary,' setting expectations about accuracy. However, it does not explain output format, rounding behavior, or clarify that the input schema expects a percent value (ratePct) rather than a state selection, despite mentioning state prefill.

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 two sentences, front-loaded with the tool's title and main purpose. Every sentence adds value: the first explains the domain, the second covers modes and the rate prefilling mechanism. No filler or redundant repetition.

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 simple 3-parameter calculator with no output schema, the description is mostly adequate, covering the domain, modes, and rate source. However, it leaves gaps: it does not specify output/return format, and the 'select a state' phrase implies an interaction not present in the API schema. This could cause an agent to expect a state parameter that does not exist, so completeness is not fully achieved.

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 0%, so the description must compensate. It explains 'mode' conceptually via 'Add or strip tax' and 'rate' as a percentage (implied by '2025 base rates'), but it does not explicitly define each parameter or mention that 'amount' is required and is the pre-tax or post-tax price depending on mode. The mention of 'Select a state to prefill the rate' may confuse because there is no 'state' parameter in the schema.

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 clearly and specifically states the tool's purpose: 'Calculate US sales tax by state' and 'Add or strip tax from any price.' This distinguishes it from sibling calculators by naming the exact resource (sales tax) and the two operation modes (add/strip, i.e., forward/reverse).

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 description gives concrete usage context: 'Select a state to prefill the rate; all 50 states included' and 'Add or strip tax from any price' clarify when each mode would be used. It does not explicitly mention alternatives or exclusions, but among the large sibling list, no other tool covers sales tax, making the intended usage clear.

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