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

Annotations already declare read-only, idempotent, non-destructive. The description adds useful context: no auth required, data source (GeoNet/GNS Science), and that the days parameter filters only the magnitude-count breakdown, not the time series. This goes beyond annotation coverage.

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?

Concise, front-loaded with the main purpose, then the parameter behavior, then data source/auth. No filler or redundant information.

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 read-only stats tool with one optional parameter and an output schema, this description covers all necessary aspects: what it returns, how to filter, data provenance, and auth requirements. Nothing 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?

Schema coverage is 100% for the single days parameter, and the description further clarifies that it affects only the magnitude-count breakdown, not the daily time series. This adds meaning beyond the schema's description.

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?

Description clearly states the tool returns New Zealand earthquake-rate statistics with magnitude-count breakdown and daily time series. It distinguishes from siblings like geonet-nz.quakes.search and detail by focusing on aggregate statistics rather than individual events.

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?

Describes the optional days filter and its effect (limits magnitude-count breakdown to one window), and clarifies that omitting returns all three windows. While it doesn't explicitly state when to prefer this over search/detail, the stats vs. events distinction is implicit.

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