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

Annotations already declare readOnlyHint=true, idempotentHint=true and non-destructive, so the safety profile is covered. The description adds useful scope: results are confined to the current billing period and include derived/estimated cost, which tells the agent the value is an estimate rather than a settled invoice.

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?

Two substantive sentences front-load the return contents, then the usage trigger. The trailing 'Example: {}' is mildly redundant given the empty schema but cheaply confirms a no-arg call.

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?

An output schema exists, so return values need not be enumerated, yet the description still summarizes payload categories, which helps intent matching. For a zero-parameter read tool this is essentially complete; only the relationship to sibling overview tools is unaddressed.

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?

Zero parameters, so the baseline is 4 by rule; the schema is empty and the description restates this with 'Example: {}', confirming no arguments are needed. Nothing further is required.

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?

States a specific verb and enumerates exactly what is returned: period calls, rate tier with per-minute limit, connected and billable accounts, and estimated monthly cost. This is clearly distinguishable from siblings like accounts_list or prubex_overview, none of which cover usage/cost.

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?

Gives an explicit trigger condition ('when the user asks about usage, limits or what Prubex costs them'), which is enough to route the agent. It stops short of naming an alternative or exclusion (e.g. vs prubex_overview), so it is clear context but not full when/when-not guidance.

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