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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses the forecast-vs-observation distinction, the returned granularity (12-hour periods over ~7 days plus hourly values), the issued_utc timestamp, a stale flag, and the US-only coverage boundary. These are all behavioral traits the annotations do not convey.

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?

Five sentences, each carrying distinct information: return type, forecast-vs-observed caveat, input options and key requirements, return shape, and coverage. The most important routing facts (what it returns, key-free vs keyed input) are front-loaded 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 and only safety-oriented annotations, the description carries the burden well: it describes return granularity, timestamps, the stale signal, and the geographic limit. An agent has everything needed to decide to call it and to construct a valid request.

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 60% and the description compensates by explaining the lat/long-vs-address alternatives and the API-key requirement attached to address, plus that periods are 12-hour blocks spanning about seven days (matching the periods default of 14). It does not clarify the hours cap of 168 or the lat/long bounds, so it stops short of a 5.

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?

The description opens with a specific verb and resource ('Returns the current National Weather Service forecast for a US point') and explicitly scopes the result as a forecast rather than observed weather, which prevents a common misreading. It does not differentiate itself from the sibling tools (get_lookup, submit_lookup), so it falls short of a 5.

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?

It clearly states the two input modes (lat/long with no key vs. U.S. street address requiring the free key) and the hard geographic constraint ('U.S. coverage only'), which is exactly the routing information an agent needs. There is no explicit when-not-to-use guidance or mention of alternative tools.

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