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

With all annotations false, the description carries the behavioral burden. It discloses non-obvious behavior: rates form series, trips use the rate in force on the drive date, no rates are preloaded, and the free tier is limited. It does not mention duplicate/replacement behavior, but the disclosed semantics are substantial.

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?

Four focused sentences with no filler: a front-loaded definition, rate-series semantics, a verification warning, and a plan limitation. Every sentence earns its place.

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 six-parameter tool with no annotations and no output schema, the description gives a coherent picture of how rates apply over time and notes the plan restriction. It is slightly incomplete on conflict behavior such as duplicate effective dates or replacement, but the agent has enough to choose and call the tool correctly.

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 100%, so the baseline is 3. The description paraphrases the six parameters and ties them to the effective-date series model, but it does not add factual detail beyond what the input schema already documents.

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?

States a specific action (set), a specific resource (mileage rate), and the precise scope (per category, jurisdiction, unit, and effective date). The first sentence alone clearly differentiates it from read-only siblings like rate_list and mileage_summary.

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 makes the tool's setting role clear and explains the rate-series context, so usage is implied rather than explicit. It does not name alternatives or state when not to use this tool, so it stops at a 3.

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