Significant earthquakes

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

Annotations already declare readOnly/openWorld/idempotent/non-destructive, so safety is covered. The description adds useful non-schema context about the returned data: times given in both UTC and Tehran (UTC+03:30) and depth_km units, which matters since there is no output schema.

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?

Two short sentences, zero waste, with the core purpose and ordering front-loaded before the usage cue and unit notes.

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 usefully discloses the time and depth unit conventions for returned fields, and the schema covers all inputs. It could go further on what fields each event carries, but for this tool it is largely complete.

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 all five parameters (days, limit, source, iran_only, min_magnitude) are already fully documented with defaults and enums. The description adds no parameter-level meaning beyond noting the output units, so baseline 3 is appropriate.

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 verb (List), resource (earthquakes), geographic scope (Iran), and ordering (largest magnitude first). This distinguishes it in spirit from eq_search/eq_latest, though it never names those siblings 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?

The phrase 'Use for "biggest earthquakes this month/year"' gives a concrete usage cue, but it offers no exclusions or routing against the four sibling tools (eq_search, eq_latest, eq_detail, eq_stats), leaving the agent to infer which one to pick.

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