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

Adds substantial context beyond annotations: cost per call, payment protocol, data source, unit coverage, and HTTP endpoint. It explains the payment side effect that aligns with readOnlyHint=false, though it does not discuss rate limits or return structure.

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?

Front-loads the core purpose and packs necessary payment details into a compact single paragraph. The payment instructions are long but earn their place for a paid tool.

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?

Covers source, units, payment, and HTTP endpoint well, but with no output schema it does not describe what current-condition fields are returned. Sibling tool differentiation is also left implicit.

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?

The two parameters have 100% schema description coverage, so the schema already defines lat/lon. The description adds no parameter-level meaning beyond the schema, which is acceptable at baseline 3.

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 resource and scope clearly: current conditions with metric and imperial units, sourced from Open-Meteo. It implicitly distinguishes from weather_forecast and weather_alerts, but does not explicitly name those alternatives.

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?

Provides invocation guidance for the paid x402 flow, including challenge/retry mechanics and the HTTP equivalent. However, it does not explicitly say when to use this tool versus weather_forecast or weather_alerts, leaving alternative selection implied.

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