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

The description discloses behavior well beyond the annotations: it is a paid tool ($0.002 USDC per successful call via x402 on Base, Solana, or Arc), failed calls are free, results are cached until the provider's expiry, and attribution/licensing terms are given. These details materially affect whether and how an agent should call it.

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?

The purpose and forecast scope are front-loaded in the first sentence, followed by source, caching, attribution, and pricing in descending order of operational importance. It is somewhat dense but no sentence is wasted.

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?

An output schema exists, so return value structure need not be explained. Given the annotations (read-only, open-world) and the paid nature of the tool, the description covers everything an agent needs: inputs, horizon, source, caching, cost, payment methods, and failure billing policy.

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 100%, so the schema already documents lat, lon, and place. The description adds only marginal semantic value by framing them as alternatives ('a place or a coordinate'), which hints at mutual exclusivity but does not state it explicitly. Baseline 3 is appropriate.

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 states exactly what the tool returns: current conditions plus 48-hour and 7-day forecasts with specific data fields (temperature, precipitation, wind, symbol), and the accepted input forms (place or coordinate). It does not explicitly distinguish itself from sibling weather_alerts, keeping it from 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 implies usage by saying 'for a place or a coordinate' and by listing the forecast horizon, but it offers no explicit when-to-use/when-not guidance and never mentions the sibling weather_alerts tool for severe-weather scenarios. Adequate but with clear gaps.

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