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

No annotations are provided, so the description carries the full burden. It discloses the one-time nature of the URL and the authentication requirement, which are meaningful behavioral traits. However, it does not mention side effects such as whether previous login URLs are invalidated, the lifetime of the URL, or how authentication failures are handled.

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 a single, well-structured sentence that front-loads the core action, followed by two short notes. There is no fluff or redundant elaboration; every sentence serves a purpose, even if some information duplicates the schema.

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?

The tool is relatively simple with two parameters and no output schema, so the description need not be extensive. It covers the core purpose, the required parameter, and the authentication prerequisite. However, it does not describe the return value (the login URL) explicitly, nor does it mention the optional sessionKey parameter, leaving gaps that an agent must infer from the schema.

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 description coverage is 50%: sessionKey has a description, but instanceId does not. The description only repeats 'Required: instanceId (string)', which adds no semantic meaning beyond the schema. It does not explain what instanceId refers to or how to obtain it, and it omits sessionKey entirely, so the description fails to compensate for the schema gap.

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 states a specific verb ('Generate'), a clear resource ('one-time login URL to the VPS control panel'), and adds context ('VirtFusion', 'for managing the server'). This distinguishes it from sibling tools like loginWithDevice or getVpsInstanceDetails, whose purposes are different.

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 to use the tool — when a one-time login URL for a VPS panel is needed — and notes that authentication is required. However, it provides no explicit guidance on when not to use it, no mention of alternatives, and no contextual selection criteria beyond the obvious use case.

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