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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, and the description stays consistent with them ('Read-only'). It adds real value beyond them: results are scoped strictly to the calling key, never another user's data, and never expose the email behind the key, and the meter spans both AT and DE under one billing point.

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 body is compact and most sentences earn their place, but the description opens with a German quoted user question before stating what the tool does, which breaks front-loading for an agent reading tool definitions. The stray indentation and mixed-language lead-in are noise a reader must skip past.

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 an output schema present, return values need no explanation, and the description still specifies the shape (totals + per-tool breakdown) and the windowing scope. For a single-optional-parameter read tool this is close to complete; only the cross-register/plan-limit terminology remains somewhat opaque.

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?

Schema description coverage is 0% and the schema supplies no enum, so the description carries the full burden – and it does, enumerating all five accepted window values (today | yesterday | month_to_date | last_30_days | all) and stating the default of 'today' as optional. Nothing about the single parameter is left ambiguous.

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 clearly states the resource and granularity: the calling key's own API usage, call count and weighted compute-units, broken down per tool. That is enough to distinguish it from every sibling (all of which return company/sector/document data). Clarity is slightly reduced by undefined jargon ('both registers', 'AT and DE', 'the facade') that an agent must infer.

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 names a concrete use case – 'check your consumption against the plan's rate limits' – plus the German example question about how many companies were queried this month, which anchors when to reach for it. No explicit when-not or named alternative is given, but the sibling set makes the boundary obvious.

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