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

Annotations already declare readOnly/non-destructive/closed-world, so the safety profile is covered. The description adds genuine behavioral detail beyond that: which families come with parent groups ('mit Obergruppe'), counts ('mit Anzahl'), and that interessen are frequent ones. It does not state the response shape explicitly, but for a read-only lookup that is a modest gap.

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 compact sentences with no filler; the purpose and the enumeration of value families are front-loaded and the optional-scoping note comes last. Nothing repeats the title verbatim.

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?

There is no output schema, so the description carries the burden of saying what comes back, and it does so at a useful level (parent grouping, counts, truncation). The residual gap is that it never says the result is meant to be fed into find_calendars' filter parameters or how values are keyed, and the 'Anlässe' mention leaves a category unexplained.

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 100%, and the schema itself explains the 'alle' default and the 60-brand truncation, so the baseline is 3. The description's own wording ('häufige Interessen und Anlässe') does not map cleanly onto the enum values, which slightly muddies rather than clarifies parameter choice.

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+resource ('Listet die gültigen Werte für die Filter von find_calendars') and enumerates the value families, which clearly distinguishes it from sibling retrieval tools like fetch/search. Minor deduction: it names 'Anlässe' as a category although the schema enum has no such value, so the list of what is returned is not fully consistent.

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?

Explicitly ties the tool to find_calendars, implying it should be called when valid filter values are needed before searching, and 'Optional nur einen Teil abrufen' gives a hint about scoped retrieval. No explicit when-not or named alternative is given, so it stops short of full routing guidance.

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