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

With no annotations, the description carries full burden but only states the conversion direction and output structure. Missing behavioral traits such as idempotency, error behavior, or whether it accepts negative amounts beyond schema constraints.

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 with clear separation of purpose and return value. Efficient but could be improved by front-loading the conversion direction more explicitly (already does). No wasted words.

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?

Given the presence of an output schema (signaled), the description mentions the return object, which is helpful. However, it lacks guidelines and behavioral details. For a simple calculator with many siblings, it is minimally complete but not thorough.

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 baseline is 3. The description adds context about the return object, which indirectly relates to parameters, but does not enhance parameter meaning beyond what the schema already provides.

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 it calculates Belgian VAT and converts between HT and TTC, with a specific verb and resource. It distinguishes from siblings like calculate_vat_generic by specifying Belgian context and the return object format.

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?

No explicit guidance on when to use this tool versus alternatives. The reference to list_bundles is indirect and does not help an agent decide between similar VAT calculation tools (e.g., calculate_vat_generic, calculate_french_vat).

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