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

Annotations already declare idempotentHint=true and destructiveHint=false, but the description adds real behavioral context: equivalent-city idempotency, alias matching, major-city precedence over same-named smaller places, and automatic catalog miss handling (Bijagua, Santorini). That is substantive disclosure beyond structured fields.

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 core action and idempotency claim are front-loaded in the first sentence, then resolution rules follow. It is dense with useful detail rather than padded, though the second sentence runs long and could be split for scanability.

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 write tool with no output schema, the definition covers input modes, idempotency, and name-resolution edge cases well. It does not state permission requirements or what the response contains when candidates are returned, leaving a small gap.

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 OR relationship between city_id and city_name and the country recommendation are already documented. The description still adds non-obvious semantics: names match the catalog including aliases, same-named cities disambiguate by country, and a missing real place is looked up and added automatically.

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 with scope: 'Add a city to the end of a trip's ordered city list.' The 'end'/'ordered list' framing cleanly separates it from trip_cities_reorder, trip_city_update, and trip_city_remove without needing to name them.

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?

Tells the agent when to supply city_name plus country and how the two input modes behave, including that ambiguous names return candidates. It stops short of naming the sibling lookup tool (cities_search) as an alternative path, so it lacks explicit alternatives/exclusions.

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