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

readOnlyHint=true already tells the agent this is a safe read. The description adds the upstream Civo endpoint and the shape of the returned payload (plan attributes including GPU), which is modest extra context. It does not mention pagination, caching, or whether results vary by region — gaps that matter for a region-scoped listing.

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?

One front-loaded sentence carrying the purpose and the return payload, followed by a short endpoint reference. No filler, no restatement of the title.

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?

There is no output schema, so the description compensates by enumerating returned fields (cores, RAM, disk, transfer, GPU), which is genuinely useful. What it omits is whether the listing is filtered by region and whether results are complete or paginated — minor gaps for a simple read-only catalog tool.

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?

Only one parameter exists and schema description coverage is 100%, with the schema fully explaining the region code, format, examples, default, and the regionality caveat. The description adds nothing about region, so the baseline 3 applies.

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') and resource ('sizes (plans)'), then enumerates the returned attributes (CPU, RAM, disk, transfer, GPU) and the resource classes they apply to (instances, Kubernetes nodes, databases). This is unmistakably distinct from sibling list tools like civo_list_instances or civo_list_volumes, which return actual resources rather than available plans.

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 'can be launched' implies this is a lookup used before provisioning, but the description never states when to call it versus alternatives or any prerequisites. The only actionable guidance (region scoping, CIVO_REGION default) lives in the schema, not the description.

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