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

Annotations already declare non-read-only, idempotent, and non-destructive, and the description is consistent with all three. It adds real context beyond them: that it returns the destination state after the change, and that unselected alternatives are preserved for comparison rather than removed. It stops short of describing failure cases or permission needs.

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 front-loaded sentences covering action, parameter rule, return value, and the anti-pattern of deleting alternatives. Slightly dense but every sentence carries necessary information with no filler.

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?

With no output schema, the description correctly explains the return value ('the destination as it now stands'), the required kind, and the select/deselect mechanics. It is complete enough to invoke correctly; only error/edge behavior (e.g., invalid optionId) is unaddressed, which is minor for this tool.

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 semantics the schema doesn't state as directly: omitting optionId is the deselect path for the given kind, and kind is mandatory because an option key alone doesn't reveal which list it belongs to. That elevates it above the schema-only baseline.

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 precise verb+resource: marking a single accommodation/transport/getting-around option as the chosen one, or clearing that choice. It clearly differs from siblings like delete_trip_item and update_destination_option by naming the selection action and the three option domains.

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?

Gives explicit operating rules: always pass the kind, pass optionId to select, omit optionId to deselect that kind. It also names an alternative behavior ('Prefer this over deleting the alternatives') and explains why, which is exactly the when-to-use/when-not guidance the dimension rewards.

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