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

With no annotations, the description carries the full burden, and it does disclose two important traits: the pay-per-call cost (0.001 USDC via x402) and the exact fields returned. However, it says nothing about rate limits, caching/refresh cadence, behavior when the upstream USGS feed is unavailable, or what happens if payment is omitted (that is left entirely to the schema's paymentProof field).

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?

Two tight sentences: the substantive data description comes first and the pricing note second. Every clause contributes either capability or cost information, with no 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?

There is no output schema, so the description usefully enumerates the returned fields (place, depth, time, tsunami flag, USGS link), and the payment mechanics are covered by the parameter schema. What is missing is a note on result volume/ordering and freshness, which an agent might want before calling.

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 all three parameters are already documented, including the 402 payment round-trip. The description restates the magnitude threshold and the 24h/7d window rather than adding new meaning, which is the expected baseline when the schema does the work.

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 (earthquakes), a data threshold (magnitude 4.5+) and a scope (last 24 hours or 7 days), plus the fields returned and the upstream source (USGS). Nothing in the sibling list covers seismic data (weather and space_weather are distinct), so an agent can select this without ambiguity.

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: an agent infers it should call this when it needs recent significant earthquake data. There is no explicit statement of when to prefer this over alternatives, no note about data staleness, and no mention of how the day/week choice should be made beyond the parameter default.

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