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

Annotations already cover read-only and open-world behavior, and the description adds real value beyond them: the data source is the page's embedded state JSON, no public API exists, and billing is $0.002 USDC per successful call via x402 with failures not charged. It does not state pagination behavior beyond 'first results page' or rate limits.

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?

Two sentences, front-loaded with the resource and returned fields, then the source mechanics and price. The field enumeration is slightly dense but every clause carries information the agent needs.

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 not be explained; the description covers data source, cost model, and geographic/scope limits. It could still say more about coverage (sale only, Barcelona city vs metro) but is sufficient to call correctly.

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 100% and the single 'limit' parameter is fully documented in the schema (1-30, default 10), so the description need not repeat it. It adds no extra meaning about the limit's effect on results.

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 resource (Barcelona homes for sale from habitaclia.com), enumerates the returned fields, and pins the scope to the first results page. The named source site alone distinguishes it from the many other real-estate sibling tools.

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?

Scope is implied by 'Barcelona homes for sale' and 'first results page', so the agent can infer the narrow use case, but there is no explicit when-to-use guidance and no named alternative (e.g. idealista-style sibling) for broader or rental searches.

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