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

Annotations already declare readOnly/idempotent/non-destructive, so the description only needs to add context — and it does, disclosing the holiday computation basis (Gauß Easter formula) and a data vintage (Stand 2026-08-15), which tells the agent how trustworthy results are for future years. It stops short of stating error behavior for invalid state/mode combinations or out-of-range dates.

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?

Purpose, modes and the sibling exclusion are front-loaded in the first two sentences, which is exactly the right ordering. The trailing list of example user questions is somewhat long and largely paraphrases the mode description, but it does aid retrieval matching.

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 takes on the return-value burden and does so by stating it returns either a working-day count or a target date. Combined with mode semantics, holiday basis and the sibling exclusion, an agent has enough to call it correctly; only error and boundary behavior remain 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?

Schema description coverage is 100%, so every parameter including the mode enum and the samstag flag is already documented in the schema; the description's restatement of add/count semantics duplicates rather than extends it. No additional syntax or edge-case guidance (e.g. end-date behavior when tage lands on a holiday) is added, so the baseline 3 applies.

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 (working-day count or target date), scopes it to the 16 German federal states with the full state-specific holiday set, and explicitly names the sibling that handles the adjacent case (vergabe_fristen_berechnen for procurement deadlines). An agent can distinguish it from the other vergabe_* date tools without opening a 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 routing rule: procurement-law deadlines count calendar days under VO 1182/71 and belong to vergabe_fristen_berechnen, not this tool. It also names the two modes and the question shapes each serves, plus concrete example queries, leaving nothing to inference.

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