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

Annotations already indicate read-only, idempotent, non-destructive. The description adds valuable context about the premium nature and cost ($0.25 USDC via x402), which is a key behavioral disclosure for cost-sensitive agents. It also mentions the decomposition of the rate into components, which is a behavioral detail not in annotations or schema.

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 compact, two sentences plus cost info. It front-loads the core purpose and input flexibility, then adds the accuracy tip and cost. It is not overly verbose but could potentially be trimmed, though the cost note is essential for a premium API.

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 only one parameter, fully documented in schema, and read-only annotations, the description covers the essentials. It lacks explicit mention of the return format, but since there is no output schema, the description could benefit from stating what the response contains (e.g., breakdown object). However, for a simple lookup tool, the current completeness is adequate for most agents.

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?

The input schema already thoroughly documents the 'lookup' parameter with a description and example. The description adds value by reiterating the accepted input formats and emphasizing that a full address yields better accuracy. Since schema coverage is 100%, the description's contribution is marginal but still helpful.

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 states the tool retrieves US sales and use tax rates and breaks down the components (state, county, city, special district, combined effective rate). It also specifies acceptable inputs (address, ZIP, city, state). This distinguishes it from tax-related siblings like interzoid_eu_vat_rates and interzoid_customs_duty_rates, which are different tax types.

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 explicitly recommends submitting a full street address for the most accurate rate assignment, guiding usage. It doesn't explicitly state when not to use it, but the distinction from EU VAT and customs duty rates is implied by the US scope and the nature of the taxes. No alternatives are named, but the context is clear.

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