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

With no annotations, the description carries the full load and does disclose key traits: cost ('FREE'), fixed non-configurable filters, and crucially that results are truncated to the top 3 by magnitude — an agent would otherwise wrongly treat this as a complete list. It omits auth expectations and behavior for a non-US or invalid ZIP.

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?

A single sentence, front-loaded with the cost signal and then the scope, with no filler. Every clause conveys a constraint the agent needs.

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 one-parameter tool with no output schema and no annotations, the description covers cost, filtering, radius, time window and result truncation. The remaining gap is what fields come back and what happens on an invalid or non-US ZIP, which is minor but not trivial.

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 coverage is 0% — the single 'zip' parameter has no description at all — so the description must compensate, and it does: it establishes that zip is a US ZIP and that it acts as the geographic center of a 100 km radius. That is enough to use the parameter correctly, though it doesn't document the accepted format.

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?

Names a concrete resource (earthquakes) and pins down the scope exactly: M2.5+, 100 km radius, 30-day window, top 3 by magnitude. An agent knows precisely what it gets. It never names the sibling seismic_history to contrast with, so it falls short of a 5.

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?

There is no explicit when-to-use or when-not-to-use statement, and the sibling seismic_history is never referenced. The hard-coded 'last 30 days' and 'top 3' constraints do implicitly signal that this is for recent, quick lookups rather than historical research, but the agent must infer that.

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