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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description reinforces this with an explicit negative list: does not send, persist, order, reserve, take payment, or collect personal details. That is genuinely useful disambiguation for an agent worried about side effects, though it does not explain the handoff mechanism.

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?

Two sentences, both load-bearing: the first states inputs and the continuation, the second enumerates non-effects. Slightly compressed phrasing but zero filler and front-loaded constraints.

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?

An output schema exists, so return values need not be described, and the safety profile is covered by both annotations and the explicit negative list. The remaining gap is routing against the two sibling tools, which the description does not address.

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 25% (county alone is documented), so the description must compensate, and it does: it names fuel, the 300–5000 range with 'whole litres' (clarifying integer semantics), and timing preferences (urgency). Enum values themselves are left to the schema, which is acceptable.

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 names the concrete inputs it prepares (county, fuel, litres, timing) and states the outcome is a handoff to 'continue on Tankful', which fits the 'draft' name. It never says what the tool actually returns (a review step, a deep link), so the agent knows the domain but not the artifact.

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 'then continue on Tankful' implies this is a first step in a flow, but neither sibling (tankful_county_price_guide, tankful_find_suppliers) is named, and there is no statement of when to pick this versus them. Usage is inferable but not guided.

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