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

Annotations already establish read-only, idempotent, non-destructive behavior, so the description's additional clarification that VPT is the tax authority's valuation rather than the purchase price is useful. But it does not disclose return format, rate-source assumptions, or error cases; with the safety profile covered by annotations, this is adequate but not rich.

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 front-loaded sentences with no fluff: the first defines scope and calculation, the second prevents a common input mistake. It loses a point only because the VPT clarification partially repeats the schema's 'Not the purchase price' note.

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 two-parameter calculation with strong annotations, the description covers the main inputs, the property type, the single-municipality limit, and the VPT-vs-price trap. It does not state the return value's format or currency, but 'yearly IMI' makes that largely inferable; no output schema exists, so a bit more return clarity would make it fully 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%, so the baseline is 3. The description reinforces that 'vpt' is not the purchase price and tells the agent to ask the user for it, adding slight value, but it offers no format/range details for either parameter that the schema doesn't already provide.

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 and resource: 'Yearly IMI for an urban property' from a taxable value (VPT) at the municipality's urban rate. It clearly identifies the calculation target and scope, but does not explicitly reference sibling tools such as imi_rate or imt_calculate, so differentiation relies on the agent recognizing 'yearly IMI' vs the other tax tools.

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?

It conveys clear contextual guidance: the tool is for one municipality's urban property and the user should provide VPT rather than the purchase price. However, it never states when to prefer this tool over siblings, nor gives exclusions (e.g., rural properties or multi-municipality cases), leaving when-to-use vs alternatives implicit.

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