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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered. The description adds useful behavioral context: the data frequency (monthly for the last year, annual before that) and the house-only restriction. It doesn't disclose return format or pagination, but for a read-only series endpoint with annotations covering safety, a 3 is appropriate.

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?

The description is two sentences with zero waste. The core purpose and temporal granularity are front-loaded, the house-only restriction is stated, and the pricing note is a single compact line. Every sentence earns its place.

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 single-parameter read-only tool with annotations covering safety, the description is mostly complete. It tells the agent what the tool returns (modelled value over time), the frequency, and the house-only restriction. However, it doesn't mention what the response looks like (no output schema exists) or how to handle the 'no series' case for units, which could leave an agent uncertain about error handling.

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 0%, so the description carries the burden for the single parameter, gnaf_id. The description does not explain what gnaf_id is or how to obtain it, but the parameter name itself is fairly self-explanatory (a G-NAF identifier). With only one parameter and a clear name, the baseline is 3; the description adds no additional semantic detail beyond the schema.

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 states a specific resource ('modelled property value over time') with a clear verb ('modelled'), and adds temporal granularity (monthly for the last year, annual before that). It distinguishes itself from sibling valuation tools by noting 'Houses only — units have no series', which helps differentiate it from properties_valuation_avm and properties_valuation_all. However, it doesn't explicitly name a sibling alternative, so it falls 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?

The description gives clear context on when the tool applies: it is for houses only, and units are excluded. This is an explicit exclusion that helps an agent avoid calling it for units. It doesn't name alternative tools for units or other valuation series, but the exclusion is strong enough to guide basic routing.

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