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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior, so the description's job is to add context. It does so well by noting there is no auth, data is USGS public domain, updates are real-time, and some volcanoes may be temporarily excluded during equipment outages. This adds meaningful behavioral nuance beyond the annotations without contradicting them.

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?

Four sentences, each earning its place: scope, return fields, caveat about instrumentation outages, and workflow/auth/update context. The most decision-relevant information is front-loaded.

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?

The tool is simple, has one optional parameter, rich annotations, and an output schema. The description covers what is returned, approximate size, caveats, intended workflow, auth requirements, and data freshness. Nothing essential is missing for an agent to invoke it correctly.

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%, and the single optional limit parameter is fully documented in the schema with range and default. The description does not add parameter-level detail beyond confirming ~69 volcanoes, so the baseline of 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?

The description opens with a specific verb and resource: 'Get all US volcanoes currently under active monitoring by the USGS Volcano Hazards Program.' It clearly distinguishes itself from detail/notice lookup tools by framing this as the first step to identify volcano IDs, and the 'monitored' scope differentiates it from volcano.status.elevated.

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 description explicitly tells agents when to use this tool: 'Use as a first step to identify volcano IDs for detail/notice lookups.' It provides clear context and workflow guidance, though it does not explicitly name alternatives or state when not to use it versus sibling tools such as volcano.status.elevated.

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