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

No annotations are supplied, so the description carries the full burden. It does disclose two real behavioral traits — a PRO subscription requirement and a hard 25 postcode limit — but says nothing about what happens when the limit is exceeded, error behavior, or rate limits.

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?

Two short sentences with no filler, and the tier flag is front-loaded before the functional statement. Nothing could be removed without losing meaning.

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?

Given no output schema, no annotations and only 2 parameters, the description covers the essentials: what is returned (current conditions, today's forecast), the input domain (postal codes) and the batch ceiling. Details like units, returned fields, and geographic coverage remain unstated but are minor for a simple read tool.

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 50%: access_token is documented in the schema but postal_codes is bare. The description contributes the important 25-item maximum for the array, yet leaves the postal code format and country/region coverage entirely unspecified.

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 current conditions plus today's forecast for a bounded set of postal codes. The postal-code scope and the 25-item cap implicitly separate it from the sibling tools forecast and forecast_full, though neither sibling is named.

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 'PRO' marker signals a paid-tier prerequisite and the 25 postal code cap implies batch use, so the intended context is inferable. However there is no explicit when-to-use framing and no statement of when an agent should prefer forecast or forecast_full instead.

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