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

Annotations already state readOnlyHint, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description still adds useful behavioral context: it asserts this call 'never spends money' (material reassurance for a billing/balance tool) and states there are no arguments, so an agent knows the call is a fixed request rather than something parameterized.

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?

Three short clauses, front-loaded with what is returned and followed by when to use it and the no-arg/read-only guarantee. Every sentence carries distinct information with no filler.

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 responsibly names the return fields (email, balance in cents and formatted) and the currency, which is the key information an agent needs to interpret results. It is nearly complete; only an explicit relationship to sibling tools like get_plan 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?

There are zero parameters, so there is nothing semantic to explain; the description's explicit 'Takes no arguments' correctly confirms the empty schema. Baseline 4 is appropriate for a parameterless tool.

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 a specific verb and resource ('Get the email of the Prokso account... and its current balance in USD (in cents and formatted)') and enumerates exactly what comes back. That clearly separates it from siblings like get_plan and get_prices, which sound billing-adjacent but return different resources.

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?

'Use it to confirm the account or before suggesting a purchase' gives concrete triggering situations rather than a vague 'use when needed'. It stops short of naming an alternative or an exclusion (e.g., when to prefer get_plan), so it earns a 4 rather than a 5.

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