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

With no annotations, the description carries the disclosure burden and does reasonably well: 'Returns' signals a read operation, and it explains the meaning of the isEntry/isExit flags plus the authentication requirement and that the key is sent automatically via x-api-key. It does not mention whether the list is paginated or how large it may be.

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 short sentences, front-loaded with the core action and return content, followed by field semantics and auth. No redundancy or 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?

For a zero-parameter lookup with no output schema, the description explains what comes back (IDs, titles, entry/exit flags) and the auth prerequisite, which is enough to call it correctly. Minor gaps are pagination and result ordering, neither of which blocks a correct invocation.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline applies. It usefully spends its words instead on the response fields that matter.

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 ('Returns destination IDs and titles') and immediately frames its role in the wider workflow (supplying port_entry_id and port_exit_id for bookings). This makes it clearly distinguishable from siblings like list_festivals, list_itineraries, and list_endpoints.

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 gives a concrete usage context: use this to obtain IDs that feed into booking entry/exit ports. It doesn't name an alternative or state when not to use it, but for a simple lookup tool the downstream-consumption guidance is sufficient.

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