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

No annotations exist, so the description carries the burden. It discloses authentication requirements, a mutually exclusive argument constraint, the default of includeEol, and the fact that template ids are per-install and change over time. It stops short of describing error behavior when both/neither key is passed, but the disclosed traits go well beyond a minimal 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?

Every sentence carries operational value: the auth constraint, the two mutually exclusive argument paths, the non-interchangeability warning, the optional flag default, and the ID-stability warning. Though fairly long, no sentence is redundant and the key constraint 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?

For a tool with no output schema and no annotations, the description gives everything needed to select and call it correctly: when to use each key, where to get those keys, what to pass to downstream tools, and a warning against hardcoded IDs. The only omission is return-value shape, which is secondary for invocation.

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 covers only sessionKey (25% coverage); the description compensates by explaining packageId (source and pre-order use), instanceId (source and reinstall use), and includeEol (boolean, default false). It also explains the relationship between the two alternative keys, adding meaning the schema lacks.

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?

Description opens with a clear verb and resource: 'List operating system templates available to install.' It distinguishes itself from siblings by naming related VPS tools (listVpsPackages, listMyVpsInstances, orderVps, buildVpsInstance) and framing the tool as the resolver for OS template ids. The purpose is unambiguous.

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?

It explicitly states 'Pass EXACTLY ONE of' and gives two distinct scenarios: packageId before ordering for orderVps, instanceId for reinstalling with buildVpsInstance. It also warns the two are not interchangeable, telling the agent to choose based on what it is about to do. This is more explicit than typical alternatives guidance.

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