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

With no annotations, the description carries the full burden and does well: it names the data provider (MET Norway) and, unusually, discloses the paid-access model ($0.002 USDC on Base or Solana via x402), which is critical behavioral context an agent must know before calling. It omits rate limits and failure behavior, keeping it out of 5 territory.

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?

Labeled Input/Output/Data/Example/Price blocks are well front-loaded and easy to scan, with the usage condition leading. The inline example query is useful; the price sentence is slightly tangential but earns its place given the payment requirement.

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?

No output schema or annotations exist, so the description must describe returns, and it does: current fields, hourly series, and daily aggregates. Combined with the data source and payment model, an agent has enough to call it correctly; pagination/error handling is the only notable gap.

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 baseline is 3, but the description adds the 0-72 range constraint on hours that the schema omits, and reinforces the defaults (24 hours, UTC). It also explains that tz affects 'daily summaries,' adding meaning beyond the schema's field description.

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+resource (worldwide weather forecast) and enumerates the exact payloads returned (current, 72h hourly, 10-day daily). The phrase 'anywhere in the world' explicitly distinguishes it from the sibling kr_weather_forecast, which is region-scoped.

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?

'Use when an agent needs the weather anywhere in the world' gives a clear triggering condition and, via 'anywhere,' implies the contrast with the Korea-specific sibling. It stops short of naming kr_weather_forecast as the alternative or stating when-not to use this tool.

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