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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is covered. The description adds the attribute set returned (price, price/m², sun score, nearby amenities), which is useful, but the 2–4 bound merely restates the schema's minItems/maxItems. Nothing about perf, pagination, or failure modes on unknown ids.

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 opens with the trigger condition and then enumerates the comparison dimensions. The parenthetical translated keywords are slightly cluttered but serve intent matching, so waste is minimal.

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 partly compensates by listing what the comparison returns. Combined with 100% schema coverage on both inputs, an agent has enough to invoke it correctly; only edge behavior (fewer than 2 or duplicate ids) is unaddressed.

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%: ids (from search_listings) and language (default de, use the user's language) are fully documented in the schema itself. The description adds no format or constraint detail beyond what the schema already gives, so 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?

Specific verb (compare) plus resource (listings), with the exact cardinality (two to four) and the full attribute set compared side by side. It is clearly distinguishable from search_listings and get_listing, which retrieve rather than compare.

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?

"Use this when someone wants to compare two to four listings" gives an explicit trigger, and the multilingual cues (vergleichen, comparer, confrontare) help match non-English user intents. No alternative tool is named or excluded, so it stops short of a full when/when-not routing rule.

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