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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint false, and openWorldHint false, covering the safety profile. The description adds a return-shape sketch, but an output schema exists, so this is redundant and adds little behavioral context beyond the annotations.

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 purpose. The return-shape listing is redundant given the output schema, slightly reducing efficiency, but the definition remains tight and easy to scan.

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 simple read-only calculator with a full schema, output schema, and rich annotations, the definition covers purpose and scope. It omits routing guidance against the many VAT-specific siblings, which is a meaningful gap in a large toolset.

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%; all three parameters have descriptions (mode enum ht/ttc, rate in %, amount). The description's 'custom rate' does not add syntax or semantics beyond what the schema already provides, so 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?

States a specific verb and resource: 'Calculate VAT/GST/sales tax' and scopes it to 'any country with custom rate'. However, it does not explicitly distinguish this generic tool from close siblings like calculate_vat_reverse or the many country-specific VAT calculators beyond the word 'generic'.

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?

Provides implied usage via 'for any country with custom rate', which suggests using this when a custom rate is needed. But it gives no explicit when-to-use or when-not guidance and does not name alternative VAT tools such as calculate_french_vat. The list_bundles pointer is a cross-reference, not routing guidance.

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