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

Annotations already establish readOnly/idempotent/non-destructive, so the description's added value is output behavior: it warns that local taxes and surtaxes are 'listed, not added' and that only the state portion is computed. It also cites the source of truth (state statute, summarized on payotte.com/usa), which is meaningful provenance. It does not discuss staleness or rate-limit concerns, but it goes well beyond the annotations.

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?

One dense paragraph, front-loaded with the jurisdiction marker ('UNITED STATES') and the core question answered. Nearly every clause carries scope information, though the long enumeration of covered topics is close to the point of being a list rather than prose.

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 no output schema, the description carries the burden of describing returns, and it does so by enumerating the fields conceptually (rate, county/city taxes, mortgage taxes, exemptions, custom payer). The data source is named. Only a brief note on units/format or data vintage is missing.

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 baseline is 3, but the description adds real semantics: `price` triggers a computed state-portion figure and only works 'when the rule reduces to one formula,' with local elements explicitly excluded. That clarifies the limits of the parameter beyond the schema's terse 'Optional purchase price in US dollars.'

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 resource (US real estate transfer tax) and enumerates exactly what it covers: whether a charge applies, the state rate, county/city taxes, mortgage taxes, exemptions, and who pays by custom. The parenthetical aliases (deed tax, documentary stamps, conveyance tax) sharpen the intent, but no sibling such as property_tax_us or closing_costs_us is named to disambiguate explicitly.

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 explains the conditional behavior of the optional `price` argument ('With `price`, computes the STATE portion...'), which is genuinely useful invocation guidance, but it never states when to prefer this tool over adjacent ones like property_tax_us (annual tax) or closing_costs_us. Usage is therefore implied rather than stated.

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