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

Annotations already communicate that the tool is read-only, idempotent, non-destructive, and open-world. The description adds the demo-mode limitation for 2026, which is useful behavioral context, but it does not describe output shape or rate categories. With annotations carrying the safety profile, this is adequate but not rich.

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 short sentences, front-loaded with the main purpose and followed by the key constraint. Every sentence earns its place, with no redundant or filler content.

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 one-parameter read-only lookup with strong annotations, the description is largely complete: it states what the tool returns and the main year limitation. It does not specify output format or rate types, but the name, title, and schema make this a minor gap for correct invocation.

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 schema provides the year parameter's type, default value, and required status, but schema description coverage is 0%. The description adds meaningful parameter context by stating that demo mode is limited to 2026, helping an agent choose a valid year in demo conditions.

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 clear action and resource: 'Return mileage-rate reference values.' This distinguishes it from sibling tax tools like tax_standard_deduction, tax_federal_brackets, or tax_calculate, which serve different reference purposes.

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?

No guidance is given about when to prefer this tool over alternatives, and no exclusions are stated. The only usage-adjacent note, 'Demo mode is limited to 2026,' is a constraint rather than a routing guideline.

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