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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and a closed-world source, so the safety profile needs no restating. The description adds information the annotations do not: that results are the current TrinkwV 2023 set and that each entry carries unit, type classification and legal reference. It does not say how many entries come back or in what order, which keeps it below a 5.

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?

A single front-loaded sentence that identifies the source, the version, and the payload fields with no filler. It is a noun phrase rather than a full sentence, but nothing in it is wasted. Slightly more structure (e.g. stating that no input is needed) would have made it airtight.

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 reference lookup with full annotation coverage and no output schema, the description carries the right load by enumerating the returned fields. What remains unstated is scale (how many parameters) and whether the data is fixed to one jurisdiction. Those gaps are small for a tool this simple.

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 there is nothing for the description to disambiguate and the baseline of 4 applies. The absence of any input is consistent with a fixed reference table and is not contradicted anywhere.

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 names a specific resource (the currently valid limit values of the German Drinking Water Ordinance, TrinkwV 2023) and the fields returned (unit, type as limit value vs. indicator parameter, and reference). This is clearly a static regulatory-reference lookup and is distinguishable in substance from measurement-oriented siblings such as get_water_quality. It stops short of explicitly contrasting itself with any sibling by name.

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?

Usage is only implied: an agent can infer this is the tool for regulatory thresholds rather than measured values. There is no explicit statement of when to use it versus get_water_quality, verify_claim, or compare_cities, and no note about whether historical or other-country limits are out of scope. The phrase 'heute geltenden' (currently valid) hints at a scope boundary but does not spell it out.

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