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

Annotations already cover read-only/idempotent/closed-world, and the description adds substantial behavior on top: provenance (GOV.UK per-country table, authority page + check date, `confidence: "secondary"`), the critical absent-vs-zero rule, that mph limits sort by km/h equivalent, and that every response carries a disclaimer. This is more disclosure than the annotations could carry alone.

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?

Front-loaded with what a visitor gets, but the entire definition is a single dense paragraph of roughly 180 words packed with semicolons and parentheticals, which is hard to scan for mode selection. Everything is arguably load-bearing, yet the wall-of-text form hurts retrieval and reading.

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 shape needn't be re-explained; the description instead covers scope (41 countries), data provenance, staleness caveat, and the absent-vs-zero edge case. Nothing an agent needs to call this correctly is missing.

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 100%, so the baseline is 3, but the description adds real meaning: `speedUnit` is the unit signed locally and never converted, `bacNote` holds novice/professional limits while 0 is a genuine zero-tolerance rule, `idpRequired` reflects a UK-photocard GOV.UK table and is absent where silent, and ranking/sort semantics for mph values. It stops short of 5 only because some schema-documented params (e.g. `limit`) get no extra color.

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 resource (driving rules) and enumerates exactly what it returns: side of road, urban/rural/motorway speed limits, BAC limit, required equipment, IDP — for a named set of 41 countries. This is unmistakably distinct from siblings like travel_advice or legal_profile.

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?

Spells out the three invocation modes clearly: `country` for one entry, `countries` for a side-by-side, and neither for a ranked list with `metric`, `sort`, and optional `drivesOn`/`idpRequired` filters. It never names an alternative sibling tool or a when-not-to-use condition, so it stops short of a 5.

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