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

Annotations already declare readOnly and openWorld, so safety is covered. The description adds valuable non-annotated behavior: USGS source, newest-first ordering, 30-day max, and especially the x402 payment model with $0.002 per successful call and no charge on failure — pricing is a material calling consideration an agent must know.

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?

Three tight sentences: data/source first, filtering second, payment last. Every clause carries information and there is 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?

An output schema exists so return values needn't be explained, yet the description still lists key fields helpfully. Pricing, source, ordering and limits make the definition callable as-is; only minor gaps like pagination via limit behavior remain.

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%, with all six parameters documented including ranges and defaults. The description adds the lat/lon/radius correlation and 'days back (max 30)' which restates schema, so little extra value beyond the baseline.

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+resource (recent earthquakes from USGS), enumerates returned fields, and describes filtering dimensions. It's clearly distinguishable from siblings like disasters, weather, or tides.

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?

Explains filtering options and the 30-day cap, which implies when this tool is appropriate (recent seismic activity). No explicit exclusion of alternatives like disasters, but the data source and field list provide strong context.

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