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

With annotations already covering readOnly/idempotent/non-destructive/closed-world, the bar is lower, and the description adds genuinely non-annotated context: the exact nature of the returned payload (plans, live prices, checkout link). It stops short of 5 by omitting error behavior for an unknown id and any indication of response size or format.

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 with zero filler; the payload contents are front-loaded and the id-provenance constraint follows immediately. Every clause carries 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 one-parameter read tool with fully documented schema and complete annotations, and with no output schema in play, the description covers purpose, sourcing of the id, and the shape of the result. Only failure modes for a bad/missing id are left unstated.

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% and the single parameter is fully documented there, including its example value "esim-japan". The description's "The id comes from search" restates the schema's provenance note rather than adding format or validation detail, so the 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?

The description conveys retrieving a single destination and enumerates the payload (plans, live prices, a checkout link per plan), which is far more specific than a name/title restatement. It falls short of 5 because the verb is only implied by the tool name and it never explicitly contrasts itself with siblings like get_plans or search_destinations.

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 id comes from search" establishes the sequencing prerequisite and implies this is a follow-up call to a search. However, it gives no when-not-to-use guidance and does not distinguish this from siblings such as get_plans or search_destinations, leaving the agent to infer selection.

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