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

With no annotations, the description carries the burden well: it discloses that accessibility and risk are not computed and return not_available, that the score is relative to available factors, that the formula is never exposed, and that market data exists only in FR/IT/DE(NRW). It does not state what happens on an unsupported country (error vs. empty) or confirm read-only semantics, which are the remaining gaps.

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?

Front-loads the output definition before the coverage caveats, which is the right order. Slight redundancy in both enumerating countries and then saying other countries are unsupported, but every sentence otherwise adds 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?

No output schema exists, and the description fully compensates by defining the score range, the rating enum values, and the factor-level values the caller will receive. Combined with the country coverage caveats, an agent has everything needed to call 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 coverage is 100% and the enum already lists ES/PV/NA/PT/FR/IT/DE, so the schema does the heavy lifting. The description restates country support but adds no syntax or behavior for 'reference' or for what auto-detect does when country is omitted — 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?

States a specific verb+resource ('Investment score (0-100) for a parcel'), the exact return shape (score, rating enum, factor levels), and how it relates to sibling data tools (solar potential via PVGIS, market data). An agent can distinguish it from get_solar_potential or get_market_data because this one composes them into a single score.

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?

Clearly bounds applicability: supported countries are enumerated and 'Other countries are not supported' is stated explicitly, plus 'One API call' sets cost expectations. It stops short of naming alternatives (e.g., call get_solar_potential directly if the score is unavailable), so it is clear context without explicit routing.

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