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

Annotations already declare readOnly, idempotent, openWorld and non-destructive. The description adds genuinely new operational context — the source is free and requires no API key — which is exactly the kind of auth/access fact annotations don't carry. It stops short of covering rate limits or default date windows.

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 with the capability front-loaded followed by the return payload and the intended use. Nothing is wasted, though the return-field list mildly overlaps the output schema.

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?

Output schema exists so return values need no prose, all three params are documented, and annotations cover the safety profile. What remains thin is query ergonomics — no mention of sort order, default time window, or result ceilings beyond the schema's max 500.

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% (limit, startTime, minMagnitude all documented with defaults and format). The description adds no parameter syntax or interaction detail, so the schema carries the full burden; 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?

States a specific verb (Query) and resource (USGS earthquake catalogue) and enumerates what comes back (magnitude, place, time, coordinates, event URL). No sibling covers seismic events, so an agent can route to it unambiguously.

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?

"Use for seismic-event primary data" implies the intended context but gives no when-not guidance, no alternatives, and no indication of how broad/global the query is. Usage is inferable rather than stated.

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