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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds real behavioral context beyond that: costs are computed from Aramco fuel prices in Saudi Arabia, an own price-per-litre can override the defaults, and the result is split between passengers. It stops short of describing the returned fields (total cost, litres, per-person share).

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 dense front-loaded sentence that packs purpose, inputs, price source and the passenger split, followed by a short reference link. Nothing is redundant, though the sentence is clause-heavy and the round-trip and unit options go unmentioned.

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 read-only calculator with full schema coverage and no output schema, the description covers inputs and price source adequately. It never states what the tool returns (total cost, litres consumed, per-passenger share) or how round_trip and unit interact with consumption, which is a real gap for a calculator whose whole value is its output.

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 every parameter including the enums for fuel and unit is already documented in the schema. The description reinforces the fuel enum and the own-price and passenger-split options but adds no formatting or interaction detail beyond that; baseline 3 applies when the schema carries the semantics.

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?

Names the computed quantity (fuel cost), the domain (car trip in Saudi Arabia), the inputs (distance and consumption) and the price sources (Aramco 91/95/diesel or own price). This implicitly separates it from the sibling saudi_fuel_prices, which returns prices rather than trip costs, though no sibling is named explicitly.

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?

Usage is implied by the phrase 'fuel cost of a car trip from distance and consumption', which tells an agent the required inputs. There is no explicit when-to-use or when-not-to-use guidance, and no pointer telling the agent to use saudi_fuel_prices when only the price is wanted.

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