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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is fully covered externally. The description adds the useful provenance detail (NGA World Port Index), but says nothing about result ordering, truncation behavior, or empty-result handling beyond what the schema's limit field implies.

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?

A single front-loaded sentence naming the data source, the resource, the key input and the optional filter. Nothing is padded and nothing important is buried.

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 simple filtered list tool with complete schema coverage and full annotations, this is nearly enough to call correctly. The only real gap is disambiguation from sibling port tools, which is a usage concern rather than a completeness one for the call itself.

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%, with country, limit and harbor_size all documented in the schema including the enum expansions, so the baseline is 3. The description restates the country formats and size letters rather than adding new meaning such as matching rules for partial country names.

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?

Specific verb (List) plus resource (NGA World Port Index ports) scoped to a country, which is clear and unambiguous. It does not, however, distinguish itself from the close siblings port_lookup and ports_near, so an agent still has to guess which port tool to pick.

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 mentions the optional harbor-size filter but gives no when-to-use guidance and never names an alternative. With three port-related siblings in the list, saying nothing about when this beats port_lookup or ports_near leaves routing to inference.

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