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

With no annotations, the description carries the full behavioral burden. It usefully discloses ordering (cheapest first), radius cap (up to 30 miles), and that results include all fuel prices and savings versus local average. However, it omits auth requirements, rate limits, and explicit read-only confirmation despite the access_token parameter.

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 a single efficient sentence with no wasted words. 'PRO.' is terse but potentially useful as a tier marker, though it slightly delays the core purpose.

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 5-parameter search tool with no output schema and no annotations, the description is partially complete: it explains return content and ordering, and the radius cap. It does not explain the limit parameter, auth flow, or how this differs from sibling tools, so an agent still lacks key context.

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 only 40%, so the description must compensate. It clarifies postcode, radius_miles cap, and fuel scope, while the schema already describes fuel and access_token. The limit parameter remains undocumented in both schema and description, leaving a meaningful gap.

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 action and resource: find all fuel stations within a radius of a postcode, sorted cheapest first, with prices and savings. It is clear what the tool does, but it does not explicitly distinguish itself from siblings like cheapest_fuel or area_benchmark.

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?

There is no guidance on when to use this tool versus alternatives, no exclusions, and no prerequisites beyond the implied postcode search. The sibling tools cheapest_fuel and area_benchmark are not mentioned, leaving the agent to infer the appropriate choice.

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