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

No annotations are provided, so the description carries the full burden. It states 'Returns HT, VAT amount,' which is basic output. It does not disclose edge cases, precision, or behavior for invalid inputs, though the schema constraints (min 0) are present. For a simple calculation tool, 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 consists of three concise sentences: the first defines the purpose, the second provides usage context, and the third directs to related tools. No unnecessary words, effectively front-loaded.

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?

The tool is simple, and the description covers its purpose, usage, inputs, and outputs (HT, VAT amount). It also references related tools for further context. With an output schema present (assumed), the description is fully adequate.

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%, with both parameters fully described (amount_incl: 'Amount including VAT', vat_rate: 'VAT rate %'). The description adds only 'Inputs: TTC amount, VAT rate %,' which does not provide additional meaning beyond the schema. Baseline 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 clearly states 'Reverse-VAT: extract the VAT and net price from a TTC amount.' It specifies the verb (extract/back out), the resource (VAT and net price from TTC amount), and distinguishes itself from sibling calculators by referencing related 'finance-france' calculators in list_bundles.

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 explicitly says 'Use to back out tax from a gross invoice,' providing clear when-to-use context. It also directs to list_bundles for related calculators, implicitly guiding to alternatives. However, it does not explicitly state when not to use this tool.

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