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

The annotations already declare readOnly, idempotent, closed-world behavior, so safety is covered. The description adds real content beyond that — registration threshold, legal basis, and that a dated lookup returns the law that set the rate — but says nothing about behavior for unsupported countries or invalid dates.

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 dense sentences, front-loaded with the resource and return contents, then the optional date behavior. Every clause earns its place; minor density at the cost of readability but no waste.

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 read tool with no output schema, the description adequately enumerates what comes back (rates, threshold, legal basis) and the effect of the optional date. The remaining gap is sibling disambiguation against get_vat_history.

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 both parameters are already documented, including the YYYY-MM-DD pattern and ISO code format. The description adds only modest meaning: that the date affects which standard rate is returned and includes the originating law, without clarifying whether the other fields (threshold, legal basis) are also dated.

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?

Names the resource precisely (VAT/GST/TVA/IVA rates, registration threshold, legal basis) and covers the multilingual aliases an agent might search for. It is clear what the tool returns, but it does not differentiate itself from the sibling get_vat_history, which overlaps with the dated-history behavior described.

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?

Usage is only implied: pass a country to get rates, pass a date to get the historical rate. There is no explicit when-to-use or when-not guidance, and no alternative tool (e.g. get_vat_history) is named despite the obvious overlap.

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