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

Annotations already declare this is a non-destructive, non-idempotent, open-world write. The description adds genuine behavioral context beyond that: no separate auth step is needed because the app surfaces the Heimster sign-in itself. It does not warn that repeat calls are non-idempotent (duplicate interest records) or describe what the user sees after registration.

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?

The purpose is front-loaded in the first clause, and the operational guidance follows in a compact second sentence. The parenthetical list of four equivalent intent phrases is bulky, but it plausibly earns its place for multilingual intent 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?

For a five-parameter write tool with no output schema, the definition covers purpose, trigger condition, optional inputs and the auth path. It stops short of describing the return/confirmation behavior and does not help the agent disambiguate from sibling enquiry tools, which is the main remaining gap.

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 only 20% (just 'language'), so the description carries real load by naming the optional phone, message and financing fields. However, it only restates the financing enum values already present in the schema and explains nothing about listing_id or what each optional field changes downstream.

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 verb ('register interest') and resource ('a property FOR SALE with the agent'), and the multilingual trigger phrases anchor the intent. It distinguishes itself from rental-oriented siblings only implicitly ('FOR SALE'), and it never names the adjacent tools apply_for_listing, send_enquiry or owner_enquiry, so the agent must infer the boundary.

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?

'Call it directly once they confirm' gives an explicit trigger condition, and the note that sign-in is handled by the app removes a prerequisite the agent would otherwise feel obliged to check. It offers no explicit when-not-to-use guidance or named alternatives among the many enquiry-type siblings.

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