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

No annotations, so the description carries the full burden. It adds genuinely useful behavioral facts the schema lacks — $0.02 cost via x402 payment and the HTTP GET shape — but does not describe the response payload, error conditions, or any rate/auth constraints beyond payment. Adequate but clearly thin for an unannotated tool.

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-loaded with the user-facing question, then the mechanics, then differentiation. Every sentence earns its place except the bracketed HTTP/price/docs metadata, which is useful but slightly cluttered in trailing position.

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 two-optional-parameter read tool with no output schema and no annotations, the description covers what it returns (rain probability and expected conditions across the window), the default behavior, cost, and endpoint. Missing only finer return-shape detail, which is a modest 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%, with defaults ('start + 6h', 'top of the next hour') and the 12-hour cap already documented per-parameter. The description's mention of pass/omit mirrors the schema rather than adding format or timezone guidance, so baseline 3 applies.

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 question-verb and resource (rain probability for Detroit across an event window) and explicitly distinguishes itself from the base sibling via 'Same shape as /v1/forecast/window with the Detroit coordinates built in.' An agent can tell it apart from weather_forecast_detroit and the generic weather_forecast-window without opening schemas.

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?

Gives clear usage context ('built for scheduling decisions') and the optionality rule (pass start/end or omit them for the next six hours), which is the key invocation decision. It never states when to prefer this over weather_forecast_detroit (point) or the base window tool, so a minor gap remains.

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