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

Annotations already mark the operation as readOnly, idempotent, and non-destructive, so the description only needs to add context beyond that. It adds 'Requires authentication' and 'including resource usage,' but does not cover return format or any rate-limit/pagination behavior; this is still acceptable given the safety annotations.

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?

A single front-loaded sentence states the action, target, and an extra detail (resource usage) with no filler. The 'getVpsInstanceDetails:' prefix is slightly redundant with the tool name but does not harm clarity.

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 simple read operation with two well-documented parameters and no output schema, the description gives enough high-level context plus the auth prerequisite. It does not enumerate the returned fields, but 'detailed information... including resource usage' plus annotations are sufficient for correct 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 description coverage is 100%, and the schema already explains instanceId's provenance and the sessionKey's conditional use in detail. The tool description adds no parameter-level meaning, so the baseline 3 applies.

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 the specific verb 'Get detailed information' with a clear resource ('a specific VPS instance') and calls out 'resource usage' as included scope. It does not explicitly differentiate from siblings like getVpsPackageDetails or listMyVpsInstances, but the 'specific instance' framing distinguishes it from listing operations.

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?

There is no guidance on when to choose this tool over alternatives such as listMyVpsInstances or getVpsPackageDetails. The only contextual hint is the schema note that instanceId comes from listMyVpsInstances; the description itself gives no usage instructions or exclusions.

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