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

The description goes well beyond the annotations: it discloses pricing ($0.003/call via x402 USDC or card key), the free tier (first 25 calls), the failed-call policy, and explicitly reconciles the readOnlyHint=false annotation by explaining that calls are charged. That is exactly the kind of behavioral context annotations cannot convey.

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 description is front-loaded with purpose, scope and filters before the pricing and annotation note, and nearly every clause carries information. It is a dense single paragraph with a slight pile-up of pricing detail, but nothing 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?

With no output schema, the description compensates by listing the return fields, and it covers source, time range, filters, cost model and the annotation rationale. An agent has everything needed to decide and invoke 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 description coverage is 100%, so both parameters (period, minMagnitude) and their allowed values are already documented in the schema. The description restates those values and adds an example, which is marginally useful but largely duplicative, so the 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?

The description names a specific resource and source (recent worldwide earthquakes from the USGS) and enumerates the returned fields (magnitude, place, time, depth, coordinates, tsunami flag, USGS link), so an agent knows exactly what it gets. It does not explicitly differentiate itself from siblings such as weather or time, but the resource is unique enough that confusion is unlikely.

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 states clear usage contexts ('Use for alerts, news and travel checks') and gives a concrete invocation example (period=day, minMagnitude=4.5). There are no explicit when-not conditions or named alternatives, which keeps it out of the top band.

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