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 genuine context beyond that: prices are per-hour, per-zone, and expressed in the account's currency. It does not disclose auth requirements, caching/staleness of prices, or whether all zones are returned at once.

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?

One dense sentence leads with the core concept and itemizes coverage, followed by a short UpCloud API endpoint mapping. No filler, though the endpoint line is marginally redundant for an agent that cannot call the REST API directly.

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 and no parameters, the description does the heavy lifting by enumerating the returned price categories and their per-hour granularity, which is what an agent needs to decide relevance. It stops short of saying whether every zone is returned or how to request a single zone.

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 per the rubric the baseline is 4. There is nothing for the description to clarify, and it correctly signals the parameterless, whole-account scope implicitly through 'per zone in the account's currency'.

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 names a specific resource (prices) and enumerates exactly what is covered: per-hour plan, core, memory, storage-tier, backup, IPv4 and traffic prices, scoped to zone and account currency. It is clear but does not explicitly differentiate itself from near-neighbors like upcloud_get_billing_summary or upcloud_list_plans.

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 when-to-use guidance: no statement that this is for costing/estimation versus billing history, and no mention of the sibling tools (get_billing_summary, list_plans) an agent should weigh it against. Usage must be inferred from the noun phrase alone.

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