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

Annotations already declare this is a non-read-only, non-destructive, idempotent mutation, so the safety profile is covered. The description's implicit point that reordering is preferable to delete-and-re-add adds some context, but it says nothing about partial-order semantics, error behavior, or permissions. The important detail that unspecified keys get sorted to the front lives in the schema, not here.

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 tight sentences, zero waste, with the action stated first and the usage guidance immediately after.

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 small, fully-documented, idempotent mutation with no output schema, the description plus schema covers what an agent needs to call it correctly. Minor gap: no statement of what happens on invalid keys or whether the full destination set must be supplied.

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%, including a nested 'order' array with its own explanation of how missing keys are handled. The description adds no parameter-level meaning beyond the schema, so baseline 3 applies.

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 (rearrange) plus resource (itinerary order of a variant's destinations), which distinguishes it from update_destination and add_destination in the sibling list. It does not explicitly name a sibling tool, but the resource scope is unambiguous.

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 an explicit usage context ('use after adding stops out of order') and rules out a workaround ('instead of deleting and re-adding them'). Clear on when to use, though it never names an alternative tool or states prerequisites (e.g. trip/variant must exist).

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