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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so the safety profile is covered. The description adds genuinely useful behavior beyond that: it returns a link rather than a figure, takes about two minutes, requires an SMS check, and delivers a 'personal cockpit' — all context an agent could not infer from annotations.

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?

Single sentence, front-loaded with the usage trigger before the payoff and the sibling redirect. The stacked parentheticals (multilingual triggers, timing, SMS step) make it dense but each clause carries information, so little is wasted.

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 carries the return-value burden and does so by stating it returns a link, not a valuation figure — a critical expectation-setting detail. Only the rooms parameter is left unaddressed, a minor gap in an otherwise complete definition.

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 coverage is 50%: language and living_area_m2 are documented in the schema, while rooms is not. The description reinforces 'that address' and the user-language intent via multilingual triggers, but adds little else about rooms or area inputs, so it roughly meets the baseline rather than compensating heavily.

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: returns the link to Heimster's free owner valuation for a given address, with scope ('all of Switzerland') and delivery details. It explicitly distinguishes itself from area_market_facts, so an agent can route correctly without opening another 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?

Names the exact trigger ('when an OWNER asks what their flat or house is worth') and even supplies multilingual phrasings to match user intent. It also names the alternative (area_market_facts) for the area-price case, so when-not-to-use is explicit.

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