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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond annotations: it returns up to 100 events, sorts by time, and targets historical/geographic filtering. This is useful but does not describe full output shape or API-specific behaviors like rate limits, so a 4 is appropriate.

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 sentences, no wasted words, and the most important information is front-loaded: what the tool does, what it filters by, what it returns, and when to choose it over the feed. Every sentence earns its place.

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 a read-only search tool with no required parameters and a fully described input schema, this description covers the main invocation context: filters, result cap, sort order, and relationship to the feed. It does not detail the event fields returned or default behavior with no filters, but those are not critical for selecting and invoking 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 description coverage is 100%, and each parameter already has a clear description including defaults and coordinate meanings. The description only groups parameters into magnitude, time range, and bounding box categories, which adds marginal interpretive value but does not compensate for anything missing 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?

The description states a specific action ('Custom earthquake search') on a specific resource (USGS fdsnws) and enumerates the key filters: magnitude, time range, and lat/lon bounding box. It also distinguishes this tool from the feed by explicitly targeting historical and geographic analytical queries, which clearly separates it from sibling tools like usgs_earthquake_feed and earthquake_recent.

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?

The description explicitly tells the agent when to use this tool: 'Use this for analytical queries instead of the feed when you need historical or geographic filtering.' This names the alternative and the condition that selects this tool, leaving little to inference.

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