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

With no annotations, the description carries the behavioral burden and does well: it discloses the blend methodology, that every response labels the producing method, the NWS provenance, the HTTP endpoint, and dynamic x402 pricing ($0.01 ≤48h, $0.03 beyond). It stops short of stating auth/payment prerequisites beyond the passing 'via x402' mention.

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 is front-loaded, but the first two sentences restate the same fact ('Hourly San Jose weather forecast' then 'Hourly weather forecast for San Jose'), wasting space. The bracketed metadata block is dense but useful; overall the redundancy costs it a point.

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?

For a no-output-schema, 2-param tool the description covers return fields, method labeling, pricing, and endpoint, which is enough to call it responsibly. Remaining gaps are the undocumented units param and the hours range mismatch with the schema (168 vs 240).

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 0% for the two required params. The description only partially compensates: 'up to 168 hours out' loosely addresses the hours param but actually conflicts with the schema maximum of 240, and the units enum (metric/imperial) is never explained. It adds some meaning but leaves real gaps and one inconsistency.

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 and resource: hourly San Jose weather forecast with named output fields (temperature, precipitation probability, wind). It also differentiates the mechanism from weather_forecast-point ('same shape ... with the San Jose coordinates built in'). It does not distinguish itself from the sibling weather_forecast-window_san-jose, 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?

Usage is only implied by the city name; there is no explicit when-to-use vs weather_forecast-window_san-jose, weather_forecast-point, or the alerts tools. The pricing note (cheaper under 48h) gives a faint selection signal but no stated conditions or exclusions.

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