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

No annotations are provided, so the description carries the full behavioral burden. The leading "PRO." hints at a paid/subscriber tier and the schema documents the access_token, but the description says nothing about rate limits, error behavior when a postcode is unknown, or whether results are cached/live. It does at least disclose the shape of the aggregate returned (min/avg/max plus cheapest brand).

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 tight sentence with the core capability front-loaded ahead of the use-case clause. The cryptic "PRO." prefix costs a little clarity but adds no bloat.

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 annotations, no output schema and only a third of parameters documented, the description should do more: auth requirements, defaults for the optional radius, and what happens on invalid postcodes are all unaddressed. Adequate to identify the tool, thin for calling it confidently.

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 33% — only access_token is documented. The description partially compensates by clarifying that the radius is measured around the postcode and that results are grouped per fuel type, but it omits postcode format/region, radius units and default value.

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 verb-and-resource pair: min/average/max price per fuel type within a radius of a postcode, plus cheapest brand. An agent can tell this is an aggregate/benchmark query rather than a single-station lookup, but it never names the sibling tools (cheapest_fuel, fuel_search) to sharpen that distinction.

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?

"For pricing, expenses and mileage rates" implies a usage context but gives no explicit when-to-use versus fuel_search or cheapest_fuel, and no exclusions. The agent must infer that this is the tool for area-level statistics rather than point lookups.

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