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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely new context: the endpoint is public and requires no authentication, and prices are quoted in CAD in both hourly and monthly form — details an agent would otherwise have to discover empirically.

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 compact sentence, with the payload contents front-loaded and the access precondition second. Nothing is wasted, though the terse style leaves the 'list' verb implicit.

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 one-parameter read-only catalog tool with no output schema, the description covers return content (plans, resources, prices), units and currency, and auth requirements. Only the region filtering behavior is left to the schema, which is a minor gap.

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% and the single region parameter is fully documented in the schema, so the baseline is 3. The description never mentions the region filter, so it adds nothing beyond the structured field.

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 names the resource (plans) and specifies what each entry contains — resources and prices in hourly/monthly CAD — which is more informative than a bare 'list plans'. It is clearly distinguishable from the mutation and VM/database siblings, though it never explicitly contrasts with a catalog sibling like list_images or list_regions.

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 'Public, no key needed' clause gives useful context about when this call is safe/possible, but there is no explicit statement of when to use it (e.g. before create_vm or estimate_vm to pick a plan) and no named alternative. Usage is only implied by the catalog nature of the tool.

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