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

With no annotations, the description carries the full behavioral burden and does a good job: it discloses cost ('FREE'), temporal scope, spatial radius, geographic restriction, and result truncation/ranking ('top 3 by magnitude'). It omits data source and output shape, which keeps it from a 5.

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 tight sentence, front-loaded with the cost signal and then the scope. Every clause earns its place and nothing is redundant.

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 simple one-parameter tool with no annotations and no output schema, the description is nearly complete: cost, time window, radius, geography, and ranking are all covered. It could add a postal-code format hint and a brief note on what fields come back, but nothing essential for invocation is missing.

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?

There is a single required parameter with 0% schema description coverage, so the description must explain it. It adds that the postal code must be Canadian, which is meaningful, but gives no format example or validation hint, leaving a gap for a 0%-covered parameter.

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 the resource (earthquakes), the scope (last 30 days, within 300 km of a Canadian postal code), and the ranking/limit (top 3 by magnitude). This is clear enough for an agent to know what it returns, though it never explicitly contrasts itself with the sibling quake_search.

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 stated constraints (Canadian postal code, 30-day window, 300 km radius), but there is no explicit when-to-use or when-not-to-use guidance and no mention of the alternative quake_search tool. The agent must infer that quake_search is for broader queries.

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