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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds nothing beyond that — no note on what happens for an unknown driver, whether an empty list is returned, or any rate/auth context. The one useful clause, 'exactly one', is a parameter constraint rather than behavioral disclosure.

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?

A single compact sentence with the scope stated first. The trailing 'GetDriverSkills.' merely restates the operation and title, adding no information.

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 simple read-only lookup with full schema coverage and annotations covering safety, the description supplies enough to call it correctly. Return shape need not be explained since there is no output schema, though a note on empty results would help.

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 the baseline is 3. The description's '(give exactly one)' is a genuine addition because the schema has no oneOf/required constraint enforcing mutual exclusivity, but it is the only semantic extra and it doesn't clarify the id-vs-code tradeoff.

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 ('skills assigned to one driver') and narrows the scope to a single driver, which separates it from the sibling ecourier_list_skills. It does not name that sibling explicitly, so a reader must infer the boundary.

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 parenthetical '(give exactly one)' gives a usable calling constraint, but there is no statement of when to prefer this over ecourier_list_skills or ecourier_get_driver, and no mention of prerequisites or error cases (e.g. unknown driver id).

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