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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the bar is low; the description adds valuable domain constraints beyond them: exactly 55 covered areas, the source registry (Statbel/FPS Finance), and the suppression rule 'no median under 16 sales'. It also enumerates the returned metrics (median, sales count, 1y/10y change, latest quarters). It does not state fallback behavior when an area is uncovered.

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 but well-ordered sentence-sequence: country front-loaded, then metrics returned, then valid area granularity, then supplier and suppression caveat. No filler. Slightly packed for a single paragraph, but every clause carries information.

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 one-parameter, non-destructive read with no output schema, the description covers the essentials: what is returned, at what geographic granularity, from what source, and the reliability caveat. An agent has everything needed to call it correctly and interpret the result.

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 'area' parameter already carries concrete examples with the useful Brussels/Bruxelles disambiguation. The description adds only the '55 covered' constraint, which is a coverage note rather than parameter syntax. Baseline 3 is appropriate when the schema does the heavy lifting.

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+resource (median price of houses and apartments) with explicit geographic scope (Belgium) and data provenance (Statbel medians of recorded resale deeds). The 'BE' qualifier combined with '55 covered' municipalities instantly separates it from house_prices_au/es/in/uk and home_prices_us/mx without opening any schema.

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 required area parameter and the enumeration of valid area granularities (municipality, province, Region), but there is no explicit when-to-use guidance and no routing to alternatives such as stats_marche, compare_regions_be, or acheter_ou_louer. The agent must infer that this is the price-lookup tool rather than the market-overview tool.

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