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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered structurally. The description adds meaningful behavior: the result set is a fixed, small enumeration of ten US grid points, so no pagination or filtering concerns arise — useful context beyond the annotations.

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, zero waste, front-loaded with the resource and its cardinality before the coverage caveat and the downstream pointer.

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 an output schema present, the description needn't explain return values, and with zero parameters there are no input semantics to cover. The scope, size of the result set, and next step are all stated.

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?

There are zero parameters, so the baseline is 4 and there is nothing for the description to disambiguate. The note about consuming 'city id' in get_weather is a minor hint about downstream usage rather than this tool's inputs.

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 (List) and resource (supported US city grid points) and pins the scope to exactly ten NWS forecast locations, with 'Not worldwide coverage' explicitly bounding it. An agent can distinguish this from worldwide enumerators like list_countries without opening a schema.

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?

Gives the follow-up path explicitly ('Use city id with get_weather'), which tells the agent why to call this and what to do next. It stops short of naming when NOT to use it beyond the worldwide-coverage caveat, so it is clear context rather than full when/when-not routing.

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