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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false. The description adds meaningful behavioral context beyond annotations: results are capped at 100 events, sorted by time, and the call is an analytical query against USGS fdsnws. This helps the agent set expectations for output volume and ordering.

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 sentences with no filler. The first sentence states the tool's function and filters; the second adds return limits and usage guidance. Every clause earns its place, and the most important scoping information is front-loaded.

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 an 8-parameter, read-only search tool with no output schema, the description covers the essential decision factors: what it does, what filters are available, result limits, and when to prefer it over the feed. Minor gaps: it does not state behavior when no filters are provided (though no parameters are required) or list the returned event fields.

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 the baseline is 3. The description groups parameters conceptually (magnitude, time range, bounding box) but adds no meaning beyond what the schema already documents. It does not clarify parameter relationships, such as whether all four bounding-box coordinates are required together.

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 and resource: 'Custom earthquake search via USGS fdsnws.' It names the filtering dimensions (magnitude, time range, lat/lon bounding box) and the return behavior ('up to 100 events sorted by time'). The mention of 'instead of the feed' distinguishes it from the sibling usgs_earthquake_feed.

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 explicit usage context: 'Use this for analytical queries instead of the feed when you need historical or geographic filtering.' This clearly identifies one alternative and a condition. However, it does not address other earthquake-related siblings like usgs_earthquake_detail or earthquake_recent, so guidance is incomplete.

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