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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), and the description goes beyond them by disclosing the cost model: a few free samples per day followed by $0.005 USDC per call via x402. That is genuinely useful invocation context. It still does not explain what the response contains or how the index is applied, but with strong annotation coverage this is solid.

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 tight sentences with the core operation front-loaded and the cost caveat second. No filler, 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?

An output schema exists so return values need not be described, and annotations carry the safety profile. The description covers purpose, data source, and pricing, leaving only minor gaps such as region default behavior when the optional parameter is omitted.

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%, so all three parameters are documented in the schema and the baseline is 3. The description's 'for a region' hints at the region parameter but adds no detail on the fact that region is optional nor what default applies when it is omitted.

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 verb (index/revalue) applied to a specific resource (a past sale price, using the UK House Price Index) with a stated scope (for a region). An agent can tell this apart from a plain price lookup, though it does not explicitly name the contrasting siblings such as house-price-index or sold-prices.

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 when-to-use or when-not-to-use guidance relative to the many uk-property siblings (house-price-index, sold-prices, price-summary, area-report). The only conditional information is commercial (free samples then paid), not tool-selection guidance.

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