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

Annotations already cover read-only, idempotent and open-world traits, so the bar is lower; the description still adds value by listing the returned fields (WPI number, coordinates, harbor size/type, depths, facilities) in the absence of an output schema, and by disclosing the error behaviour when nothing matches.

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 action and lookup keys, then return payload, then failure behaviour. Every sentence carries distinct information with no 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?

With no output schema, the description helpfully enumerates the return fields and error case, making it callable without inspecting further. The remaining minor gap is that it never says whether multiple identifiers may be supplied together or which takes precedence.

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%, so the schema already documents all three parameters including the exact-match/substring fallback for name; the description only restates the lookup keys and adds no syntax or combination rules beyond the schema.

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 (look up) and resource (a port) and enumerates the three lookup keys (name, UN/LOCODE, WPI number), which functionally separates it from the geographic siblings ports_by_country and ports_near.

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 enumeration of accepted identifiers implies when the tool applies (you hold a port name/code/number), but there is no explicit guidance on when to prefer it over ports_near or ports_by_country, nor any note that at least one identifier is needed given zero required parameters.

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