List VAT exemption reasons

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is fully covered without the description. The description adds that the list is "official" and from SEF, which is modest but real context about authority and stability. It says nothing about whether the list is static or changes, or what a consumer should expect beyond codes.

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?

A single front-loaded sentence with no filler; the resource and an illustrative code are stated immediately. Nothing could be removed without losing information.

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?

With no parameters, no output schema, and rich annotations, the definition needs only to describe what comes back, and it does so only minimally — an agent cannot tell whether entries are bare code strings or objects with code plus description text. That return-shape gap is the main missing piece for a reference-lookup tool.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a 0-parameter tool applies. The mention of an example code format (PDV-RS-33) is a small bonus that hints at the value space, though not a parameter.

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?

"Returns SEF's official list of VAT exemption reason codes" gives a specific verb (returns) and a concrete resource, plus an example code format (PDV-RS-33) that makes the content unmistakable. It is clearly distinct from the invoice-writing siblings, but it does not explicitly distinguish itself from the similar reference-data sibling sef_list_unit_measures, leaving that differentiation to the name alone.

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 implies the use case — you fetch codes when you need an exemption reason for invoicing — but never states when to call this versus other tools, nor any prerequisite such as needing a configured company. Usage must be inferred entirely from the resource name.

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