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

Annotations already declare readOnlyHint, destructiveHint=false, and openWorldHint=false, but the description adds genuinely non-obvious context: nothing is sent, the agent's phone/email is never returned, and contact is routed through Cubi's consented flow. That is real behavioral value beyond the structured fields.

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?

Front-loaded summary sentence followed by the behavioral guarantee and a clean Args block. Each sentence earns its place, though the parenthetical enumeration of contact methods is slightly listy.

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 an output schema present, return values need no elaboration, yet the description still previews them usefully. Inputs, behavior, and privacy constraints are all covered; nothing an agent needs to call this correctly is missing.

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 0%, so the description carries the full load and does: listing_id is defined as the exact listing URL from a search result or a source-prefixed id like 'remax:12345', and lang is an ISO 639-1 code defaulting to en. Both parameters are fully disambiguated.

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 (lists/returns) and resource (contact methods for a listing) and enumerates exactly what comes back: contact methods, unanswered suggested questions, and start links. No sibling tool overlaps this concern, so an agent can select it unambiguously.

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 implied by the phrase 'for one Cubi Estate listing' and the listing_id input, suggesting it is called after finding a listing, but there is no explicit when-to-use statement, no exclusion, and no named alternative among the siblings.

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