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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so the safety profile is covered. The description adds genuinely non-structured context: the guide may be unavailable, and results carry an observation date and confidence level. It stops short of saying what an unavailable state looks like.

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?

Three compact sentences with no filler: capability first, reliability caveat second, scope exclusion last. Every sentence carries distinct information an agent needs.

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, three-parameter tool with a full output schema and rich annotations, the description covers availability risk and result provenance (date, confidence) rather than restating returns. Lacking only an explicit pointer to the sibling tool for actual quotes or ordering.

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 33%, but the description compensates by naming the three litre bands and the kerosene-only fuel type, matching the enum and const. The county dimension is only implied by 'county reference guide'; the schema's own note about not passing addresses/Eircodes does the remaining work.

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 (read) and resource (published kerosene county reference guide) plus the exact litre bands it serves. The closing line 'Not a supplier quote or bookable offer' separates it from tankful_find_suppliers and tankful_delivery_request_draft without needing their schemas.

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?

'May be unavailable' and 'Not a supplier quote or bookable offer' give a clear use context and one explicit exclusion, so an agent knows this is reference data only. It never names a sibling as the alternative for the excluded cases, so routing still requires inference.

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