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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable context beyond that: the data is canonical, derives from completed trips, excludes other people's travel, costs $0.10 per call, and requires an API key. No contradiction exists.

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?

The description is extremely compact and front-loaded, with the core meaning first and the cost/auth note parenthesized. All words carry value, though the phrase 'not other people travel' is grammatically awkward and 'canonical' is undefined. Overall it is efficient, not bloated.

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 three optional and completely undocumented parameters, the description does not give the agent enough to call the tool correctly. The output schema and read-only annotations help, but the missing parameter semantics and the lack of explicit date-range/format guidance make this under-specified for a tool with multiple optional inputs.

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 0%, so the description must compensate for the undocumented 'to', 'from', and 'include_residence' parameters. It does not mention or explain any of them. The agent is left to guess whether 'from'/'to' are dates, ids, or something else, and what residence inclusion means.

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 clearly identifies the resource (countries) and the source scope (completed trips), and adds a distinguishing 'not other people travel' note. It does not use an explicit verb, but 'canonical countries from completed trips' is unambiguous enough for an agent to infer a retrieval operation.

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 description implies when to use the tool (when the ask concerns canonical countries visited on completed trips, not cities or individual trips) but does not name any alternative tool or state explicit exclusions. Sibling tools like get_cities_visited or get_travel_history are present but not referenced, leaving routing to the agent's inference.

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