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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds real depth beyond that: the data source (federal GWR register), the inclusion threshold (≥3 flats), and the nature of the results (approved and ongoing projects, with size and status). It omits pagination/count behavior for limit.

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 sentence with the usage trigger front-loaded and the parenthetical multilingual synonyms placed after the core scope. Nothing is redundant, though the long trigger list makes the sentence dense.

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 read-only, idempotent, no-output-schema tool with one required parameter, the description covers what it retrieves, from where, and under what filter. The only real omission is the behavior of the undocumented limit parameter, which is a minor gap rather than a blocking one.

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 50%: place and language are documented in the schema, while limit and min_dwellings have no descriptions. The description partially compensates by stating the 'at least 3 flats' criterion that underlies min_dwellings, but it says nothing about what limit controls or its 1–15 range. Baseline 3 is appropriate for this partial gap.

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 gives a concrete verb+resource ('approved and ongoing residential projects' from GWR with ≥3 flats), plus the returned fields (size, status). It is far more specific than a restatement of the title. It does not, however, distinguish itself from the sibling search_new_builds, which an agent could easily confuse with this tool.

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?

It opens with an explicit usage trigger ('Use this when someone asks what is being built or planned in a Swiss municipality or canton') and supplies multilingual query phrasings to match against, which is directly actionable. There is no when-not guidance and no named alternative, so it stops short of routing between competing tools.

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