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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds context about what data plans contain (fixed-price, included storage/transfer, GPU details) but does not disclose any behavioral traits like pagination, result limits, or authentication needs beyond what the annotations provide.

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 sentences: one front-loaded with the resource and its fields, and one giving the API endpoint. It is appropriately sized and free of filler, though the first sentence is a fragment rather than a complete statement of the tool's action.

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?

With no output schema, the description carries the burden of explaining return values, and it does so by listing the fields included in each plan. It does not mention pagination or ordering, but for a simple parameterless list tool, the provided context is largely sufficient.

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 takes zero parameters, so there are no parameter semantics to document. The baseline score of 4 applies because the description does not need to compensate for any missing parameter information.

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 identifies the resource (fixed-price server plans) and enumerates the fields each plan contains (name, cores, memory, storage, transfer, GPU details), making the tool's data scope clear. However, it does not explicitly state the operation ('list') and does not differentiate from siblings like upcloud_list_prices, leaving the agent to infer the action from the tool name.

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 provides no guidance on when to use this tool versus alternatives such as upcloud_list_prices or upcloud_list_zones. There are no conditions, exclusions, or prerequisites mentioned, leaving the agent with only the name to infer usage context.

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