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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds value beyond that by disclosing the 2026 rule vintage and that the content explicitly includes what is *not* modelled and the official sources — useful trust signals for a reference tool. It doesn't state the return shape, but with no output schema the content enumeration largely substitutes for that.

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 sentences, front-loaded with what the tool returns and followed by the call condition. Every clause (rules, options, gaps, sources) maps to a distinct piece of content an agent would want; nothing is redundant.

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 zero-parameter, read-only reference tool with no output schema, the description covers what the payload contains, its time validity (2026), and its role versus the calculators. A small remaining gap is the absence of any indication of size/format of the reference content, but that is minor at this complexity.

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?

The tool takes zero parameters, so the baseline is 4 and there is nothing for the description to disambiguate. No misleading parameter language is present.

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 names a concrete resource — the Italy tax rules the calculators apply, the options taken, the unmodelled cases, and the official sources — which is clearly distinct from the calculator siblings (net_salary, employer_cost, etc.). It stops short of saying outright that this is a static reference/metadata tool rather than a calculator, but the content list makes that inferable.

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?

"Call it before answering a question the other tools may not cover" gives an explicit trigger and positions this tool relative to its siblings as a fallback/grounding step. The qualifier "may not cover" is hedged — it doesn't define a crisp boundary such as out-of-scope years or rule categories — so the agent still has to guess when the coverage check is truly needed.

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