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

Annotations already indicate read-only and non-destructive behavior. The description adds valuable context by explicitly stating it shows only descriptive facts (price, size, £/m²) and refrains from making judgments. This clarifies the tool's scope and limitations beyond the annotation hints, though it doesn't discuss failure modes or return format (covered by output schema).

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 description is two sentences long and front-loaded with the primary purpose. Every sentence adds value: the first defines the action and constraints, the second details the specific outputs and explicitly excludes subjective analysis. There is no redundancy or unnecessary wording.

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?

The description, combined with the annotations and output schema, provides complete context. It covers what the tool compares, the constraints (2-4, same type, active), and explicitly states what it does not do. Since an output schema exists, the description doesn't need to explain return values. All critical usage aspects are addressed.

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?

The input schema fully describes the only parameter, listing_ids, including its type, format, and count (2-4). The description does not add additional semantic meaning to the parameter itself; it only reiterates the count requirement. Since schema coverage is 100%, the baseline of 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?

The description clearly states the tool's function: comparing descriptive facts from 2-4 active Evlek listings. It specifies the resource (listings), the action (compare), the scope (same type, sale or long-term rent), and the specific outputs (price, size, £/m²). This distinguishes it from siblings like compare_cities and get_listing_detail.

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?

The description provides clear when-to-use context: comparing 2-4 listings of the same type. It also implies boundaries by stating it does not make value or investment judgments, which is a useful guideline. However, it does not explicitly mention alternatives for single listing details or city comparisons, so it lacks full exclusionary guidance.

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