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

Annotations already declare this a safe, idempotent, closed-world read, so the safety burden is offloaded. The description adds useful provenance the annotations cannot convey — data source (Ministry, INE), vintage (Q2 2026), and coverage breadth — but says nothing about caching, rate limits, or how missing places are handled.

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?

One dense sentence, front-loaded with the country identifier and packed with scope, source, period, and metrics. Nothing is wasted or repeated.

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 low-complexity single-parameter lookup with rich annotations and no output schema, the description does state which values come back (per m² value, one-year change, regional index). It stops short of describing the return structure, but given the tool's simplicity and the annotation coverage this is nearly complete.

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 100% and the single 'place' parameter already carries examples and the empty-string default in the schema. The description adds no extra syntax or semantics beyond what the schema supplies, so the baseline 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 names a concrete resource (Ministry average appraised value per m²) plus the exact coverage (55 cities, 19 regions), the change metric, and the INE index, so the agent knows precisely what data this returns. The leading 'SPAIN.' and the _es suffix separate it from the other country-level house_prices_* tools, but it never distinguishes itself from the potentially overlapping compare_regions_es sibling.

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?

There is no statement of when to pick this tool versus house_prices_uk/au/in, home_prices_us/mx, compare_regions_es, or stats_marche. The agent must infer usage purely from the country marker in the description and tool name, which is minimal guidance.

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