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

Annotations already declare read-only, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds real value beyond that: results include every observed revision, carry their data source and last-confirmed timestamp, link to both QuakeIndex and USGS event pages, and flag automatic solutions as first estimates. It stops short of stating behavior for an unknown/retired event id.

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?

Front-loaded with the core capability and the identifier form in the first clause, then the revision behavior. The final sentence about predictions/warnings is slightly tangential to retrieval but earns its place by preventing misuse of the tool as an alerting endpoint.

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?

With no output schema, the description carries the burden of describing returns and does so well (source, last-confirmed time, page links, revision history). The only gap is error behavior for an invalid or unknown event id, which an agent would want before invoking.

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 the schema already documents that id accepts a USGS event id (e.g. 'ci41234567') or an event page URL. The description repeats the same fact without adding format constraints, normalization rules, or fallback behavior, so the 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 resource (one earthquake, keyed by USGS event id or event URL) and a concrete scope: all held data including every observed revision. Sibling differentiation is implicit rather than stated — nothing names earthquakes_near, latest_earthquakes, or place_activity — but an agent can infer this is the single-event-by-id lookup versus the list/search siblings.

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 implied by the required id ('by USGS event id or URL'), so an agent knows it needs an identifier in hand. The closing sentence usefully sets expectations about what this tool will NOT return (no predictions, no warnings; ShakeAlert/MyShake are the warning sources), but there is no explicit when-to-use/when-not or named alternative for the no-id case.

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