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

Annotations cover only readOnly/openWorld/idempotent, yet the description adds the commercial and payment model (x402 USDC on Base, $0.001 per successful call, calling without payment yields a PaymentRequired object), the empty-result behavior (no alerts = 200 with count 0), and data provenance (official public-domain NWS, US only). These are material traits an agent cannot infer from the annotations.

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?

A single dense paragraph, but it is front-loaded with the use case and return shape before dropping into filters, edge-case behavior, and pricing. Every sentence carries information; only the breadth makes it feel long rather than filler.

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?

With no output schema, the description still lists the returned fields, the filter selectors (state/point/place/zone), severity and event refinement, empty-result semantics, geographic scope, and payment/error behavior. An agent has everything needed to select and call the tool correctly.

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 baseline is 3, but the description adds the framing that the filter modes are alternatives ('filter by state... by point... or by NWS zone') with concrete zone examples (TXZ211, NYC061) and notes that state codes also cover territories and marine areas. It also explains full=true vs trimmed text, which is not spelled out in the schema.

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?

Starts with a specific verb+resource ('returns the currently active National Weather Service alerts') and enumerates exactly what comes back (event, severity, certainty, urgency, affected areas, onset/expiry, issuing office). It is clearly distinguished from the sibling us_weather_forecast, which covers forecasts rather than active alerts.

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 concrete when-to-use contexts ('before travel, logistics, field work, events or outdoor plans in the US, or to monitor severe weather') and a clear scope boundary ('US only'). It does not explicitly route the agent to the forecast sibling for forecast data, so it stops short of full alternative-aware guidance.

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