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

With no annotations, the description carries the full behavioral burden; it does disclose the return shape (magnitude-band counts, strongest events, risk signal) and the years default of 20, which is genuinely useful. It does not state that the tool is read-only, what happens without a valid subscriber token, whether a paid plan gates it, or any rate limits. Adequate, but notable gaps for a zero-annotation tool.

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 front-loaded sentence with no waste; every clause adds a distinct fact (geography, timeframe, output contents). The leading 'PRO.' token is unearned mystery rather than information, which is the only structural blemish.

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 4-parameter tool with no annotations, no output schema, and 25% schema coverage, the description covers the essentials of what comes back and the years default, which is more than many. It leaves radius_km semantics, the meaning of 'risk signal' and 'magnitude band,' and any auth/tier behavior undefined, so it is workable but incomplete.

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 only 25% (only access_token documented), so the description must compensate more than it does. It contributes the years default of 20 and clarifies that zip is the location anchor, but radius_km is never mentioned and no units or bounds are given for years or radius. Partial compensation only.

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 names a concrete resource and scope: earthquake history near a ZIP over N years, with counts by magnitude band, strongest events, and a risk signal. That reads clearly against siblings recent_quakes (recent events) and sites_check, though the differentiation is implied by 'history' rather than stated. The cryptic 'PRO' prefix is unexplained but does not obscure the purpose.

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 no sibling is named. The phrase 'history near a ZIP over N years' implicitly positions it against recent_quakes, but the agent must infer that a historical/aggregate query belongs here while a current-events query belongs elsewhere. 'PRO' hints at a paid tier but never says what that means operationally.

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