list_regions

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

Annotations already cover readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is established. The description adds valuable data-semantics context (hourly vs monthly pricing and the conversion factor), which is useful but not a behavioral trait of the tool itself. It does not describe output structure or pagination, but for a zero-parameter read-only list this is a minor gap.

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 front-loads the main purpose and then spends space on an important unit conversion caveat and a warning about a previously shipped mistake. Every sentence contributes useful guidance, though the third sentence is slightly verbose and could be tightened without losing value.

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 parameterless, read-only, idempotent list tool without an output schema, the description is complete. It states what is returned (regions and associated rates), clarifies the units for each field, and warns about the known pitfall. An agent can invoke it correctly with no additional information.

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?

The tool has zero parameters and 100% schema coverage, so the description carries no parameter burden. The baseline for zero parameters is 4, and the description appropriately focuses on output data rather than input arguments.

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 precise action and resource: 'List every Point of Presence (region/data-center location) VPS instances can be deployed in'. This clearly differentiates it from sibling tools like get_vps_pricing by focusing on the enumerable deployment locations and their attached rates, rather than pricing logic or VPS-specific queries.

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 implies when this tool is useful: when a user needs the full set of deployable regions and their per-unit rates before creating a VPS. It also points to create_vps for cost explanation, which orients the agent toward the next step. No explicit exclusions or 'instead of' guidance, but the context is clear enough.

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