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

With no annotations provided, the description carries the full behavioral burden and does so excellently. It discloses rounding to the cent, half-away-from-zero convention, the reconciliation invariant (net plus tax equals gross exactly), and the acceptance of any rate from 0 to 100. These details go well beyond what the schema reveals.

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 well organized and front-loaded with the core purpose, followed by rate details, rounding behavior, and explicit exclusions. Every sentence earns its place; there is no filler or repetition of schema content.

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?

Even though there is no output schema, the description explains exactly what the agent can expect back: all three figures, rounded to the cent, and reconciling exactly. For a pure arithmetic tool with three fully documented parameters, no important calling context is missing.

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%, and the schema already documents amount, rate, and basis clearly, including the percentage interpretation and net/gross semantics. The description adds useful global context about rounding and output figures, but it does not add per-parameter meaning beyond the schema, so the baseline of 3 is appropriate.

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: it converts between net, tax and gross for a given VAT rate, in either direction. It also distinguishes itself from the sibling invoice/validation tools by explicitly saying it is 'arithmetic, not tax advice.'

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 clearly indicates when to use the tool: for VAT conversions with any rate from 0 to 100, on net or gross amounts. It also spells out what it does NOT do—rate determination, reverse charge, intra-community supply, and similar tax-rule concerns—but it does not explicitly point to alternative sibling tools for those cases.

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