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

With no annotations, the description carries the burden of behavioral context. It states that authentication is required and that results are scoped to the authenticated user's ownership, which are useful behavioral traits. It does not disclose pagination or response shape, but for a list operation this is acceptable.

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 two short sentences with no filler. It front-loads the core action and scope, then adds the necessary authentication requirement. Every word earns its place.

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?

Given the simple parameter surface and clear purpose, the description is nearly complete. It lacks an explicit statement of return format or pagination, but 'List all' implies a collection of instances, and the schema covers the only parameter.

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 only parameter, sessionKey, is already fully documented in the input schema with clear guidance on when to pass it and when to omit it. The description's authentication note is consistent but adds no new parameter-level meaning beyond the schema.

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 uses a specific verb ('List') and resource ('VPS instances') with an explicit scope ('owned by the authenticated user'). It clearly distinguishes this tool from sibling tools like countMyVpsInstances, getVpsInstanceDetails, and listVpsLocations.

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 intended use is clear: call this when you need all VPS instances for the authenticated user. It does not explicitly name alternatives or state when not to use it, but the scope is specific enough that an agent can select it correctly for listing purposes.

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