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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so the safety bar is met. The description adds genuinely new behavior: USGS real-time feeds refreshed every minute, free pricing, and that invalid input or upstream failure returns isError without charge.

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 scope, then a compact trailing clause for source, price and error semantics. Every sentence earns its place; the single long sentence is dense but not padded.

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 an output schema present and 100% param coverage, the description need not explain return values, yet it flags the key returned fields and covers cost and error behavior. Complete for an agent to call it correctly; only pagination/ordering nuance ('largest first') lives solely in the schema.

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 schema already documents all five parameters with ranges and defaults. The description only re-expresses the magnitude filter and radius condition ('only when a place is given') and maps the window to 'last hour to 30 days', adding marginal value over 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?

States a specific resource and scope: worldwide earthquakes over a look-back window, filtered by magnitude and optional place radius, returning depth/tsunami/alert fields. It is easily separable from the nearest siblings (weather, geocode, sun_moon) even though no sibling is named explicitly.

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?

Clear context for when it applies: recent quakes, magnitude floor, and radius only when a place is given. No explicit when-not-use or named alternatives, but no sibling overlaps functionally, so the guidance is sufficient for routing.

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