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

With no annotations provided, the description carries the full burden. It explicitly states 'Reads only,' discloses grouping and ordering behavior, and clarifies that it returns the full rate series. This is solid transparency for a simple list operation, though it does not describe output format details.

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?

A single sentence that front-loads the action and resource, then adds grouping and ordering details without any filler. Every phrase contributes meaning.

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 zero-parameter, read-only list tool, the description provides the essential behavioral context: what is listed, how it is organized, and that it is safe to call. It could mention return format or potential size, but nothing critical is missing 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 tool has zero parameters, and the description confirms the scope ('every mileage rate on file'), leaving no ambiguity about what the call returns. The baseline for a parameterless tool is high, and the description fully satisfies it.

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 uses a specific verb ('List') with a clear resource ('every mileage rate on file') and adds distinguishing details: grouping by jurisdiction and category, and inclusion of effective-from dates. This makes it easy to tell apart from siblings like rate_set 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 phrase 'the series each trip is priced from' gives useful context for when to use this tool: when you need the rate series used for trip pricing. It does not explicitly name alternatives or exclusions, but the context is clear enough for a zero-parameter read tool.

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