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

The annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so 'Rein lesend' largely restates structured data. The description does add that this applies to a Pay-per-Use-Konto, which is useful context, but says nothing about return format, units, or freshness of the balance.

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 core action is front-loaded in the first clause, followed by usage guidance and alternatives in a compact form. The trailing keyword tag ('| EN: credit, balance, pricing, ...') is search padding rather than information, and 'Rein lesend' duplicates the annotations.

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?

For a zero-parameter, read-only, annotation-covered tool with no output schema, the description covers what it returns (current credit balance) and when to call it. Only the shape/units of the returned balance and any caching or rate-limit behavior are unstated.

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 the baseline is 4 and there is no parameter semantics for the description to add. It correctly does not invent or imply inputs.

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 resource ('Das aktuelle Credit-Guthaben abrufen') and scopes it to a pay-per-use account. It is clearly distinguishable from the sibling credit tools (pricing, chargeup, checkout) without opening any schema.

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 when-to-use condition ('vor kostspieligen Aktionen pruefen, ob Guthaben vorhanden ist') and routes the agent to the correct alternatives: onto_credit_pricing for costs, onto_credit_chargeup / onto_credit_checkout for topping up. Nothing about sibling selection is left to inference.

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