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

With no annotations, the description carries the full burden and does disclose two operationally critical traits: the call is paid (x402, $0.002 USDC on eip155:8453) and results are cached for 30 minutes, meaning data can be stale. It also notes no API key is required. It stops short of stating rate limits, failure behavior for unknown cities, or precedence between city and lat/lon.

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 dense sentence front-loads source and returned data, then location modes, then the caching and payment constraints. No filler; every clause carries information.

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 annotations and no output schema, the description does describe the return contents (current conditions plus 3-day forecast), the data source, the cache window and the payment requirement — enough for an agent to decide whether to call it. Missing units, error behavior, and locator precedence keep it from being fully complete.

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 and the baseline is 3. The description adds the either/or intent ('by city name or coordinates'), but that framing sits awkwardly against a schema that marks city, lat and lon all as required, and it does not resolve which input wins or what units lat/lon use.

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 the exact resource and its scope: live weather from Open-Meteo including current temperature, humidity, wind, conditions, plus a 3-day forecast. It also names the two accepted locator forms (city name or coordinates), so an agent knows precisely what it gets back. No sibling tool overlaps with weather, so no differentiation is needed.

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?

Usage is only implied via the locator forms ('by city name or coordinates'); there is no explicit when-to-use, when-not-to-use, or alternative tool named. Since no sibling is a weather tool, the routing risk is low, which keeps this at an adequate-but-unstated level.

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