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

Annotations already cover read-only, idempotent, and closed-world safety, but the description adds genuine context: it works without sign-in (auth requirement) and documents how the displayed hourly price is derived (lowest monthlyCents divided by hoursPerMonth, rounded, floored at 1 cent). That derivation rule is important for interpreting results and is not in any structured field.

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 payload description is front-loaded and every sentence carries content, but the middle sentence is dense and run-on, packing the naming rule and the rounding formula together. Slightly tighter structuring would improve scanability without losing information.

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 returns and mostly succeeds: it names the price fields, the three schedules, the hourly derivation, and the region/size identifier rules. The shape of 'always-on host references when available' remains somewhat vague, but nothing needed to call the tool (it takes no arguments) is missing.

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?

With zero input parameters the baseline is 4, and the description earns it by explaining how returned values map onto another tool's parameters: name sizes by memoryGb, add vcpu when two sizes share memory, and use the size value only for createServer. This is useful semantic bridging rather than restatement.

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 return payload: estimated monthly prices in US cents for every region and size under three named play schedules, plus always-on host references. This is distinguishable from cost-related siblings like getBalance or getMonthSpending, which cover account spend rather than a region/size price catalog.

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 says to use it to quote prices or choose region and size, and links forward to createServer by telling the agent to pass a region's id (not awsRegion) and a size as size. It lacks explicit when-not-to-use guidance, which keeps it below a 5.

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