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

Annotations already establish readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real value beyond them by disclosing cost ('Free') and by enumerating the semantic content of the response (country, rent/sale, accepted filters, location syntax) despite there being no output schema. It stops short of saying whether the listing is static or reflects live account state.

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 tight sentence with zero filler; the return-content list is front-loaded and the cost note is placed last. The fragmentary grammar ('The portals search_listings can read: …') is slightly harder to parse than a clean verb-first sentence.

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 zero-parameter, read-only listing tool with an output schema absent, the description carries the needed burden by enumerating the fields each portal entry exposes. An agent has enough to decide to call it and to use the result. Only the relationship/protocol with search_listings remains implicit.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. Nothing in the text suggests hidden argument surface, which is the right signal for a no-arg call.

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 the resource (the portals that search_listings can read) and enumerates the per-portal information returned, so an agent knows exactly what this call yields. It differentiates from the only sibling by framing itself as metadata *about* the portals search_listings queries. It reads as a noun phrase rather than a verb+resource statement, which keeps it just short of a 5.

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?

Naming search_listings implies this is a discovery step to run before searching, but the description never says so explicitly and gives no when-not-to-use condition or alternative. An agent can infer the sequencing, but it must infer it.

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