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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description adds value by mentioning it is 'Keyless' and explaining the scale (0-5) and what is included (activity description, hazards, aviation colour code), which provides behavioral context beyond annotations.

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?

The description is four sentences, front-loaded with the core purpose, and every sentence provides unique information (data source, scale, included details, keyless access). No wasted words.

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 zero-parameter, read-only tool, the description is comprehensive. It covers data source, geographic scope, scale explanation, and return fields. No output schema exists, so the description substitutes effectively. Possibly missing update frequency, but not crucial.

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 are zero parameters, so the description is not required to add parameter info. However, it explains the output format and scale, which is helpful given the lack of an output schema. Baseline 4 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?

The description clearly states it provides 'Current Volcanic Alert Levels for all monitored New Zealand volcanoes' from GeoNet, distinguishing it from USGS. The name and title match. Among siblings like get_quake or recent_alerts, this tool is uniquely positioned for NZ volcano alerts.

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?

Implicitly, the description suggests using this tool for NZ volcano data where USGS doesn't cover, but it doesn't explicitly state when to use versus alternatives or when not to use. The context is clear enough for an agent.

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