get_vat_rates

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It effectively describes what the tool returns (multiple VAT rates and surcharges), mentions the source (Ley 37/1992 del IVA) for credibility, and implies it's a read-only operation through 'Returns.' However, it doesn't specify rate limits, error conditions, or response format details that would be helpful for an agent.

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 efficiently structured in three sentences: purpose, scope, usage guidance, and source. Every sentence adds value without redundancy. It's front-loaded with the core functionality and includes necessary details concisely.

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 tool's moderate complexity (2 parameters, no output schema, no annotations), the description is mostly complete. It covers purpose, scope, usage guidance, and source. However, without an output schema, it could better describe the return format (e.g., structured rates by category) to help the agent interpret results.

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%, providing a strong baseline. The description adds some value by explaining the meaning of territory parameters ('canarias' for IGIC, 'ceuta_melilla' for IPSI), which goes beyond the schema's enum values. However, it doesn't provide additional context about the 'year' parameter or clarify the output structure beyond rate types.

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 the specific action ('Returns Spanish VAT (IVA) rates'), resource ('for a given fiscal year'), and scope ('Includes general, reduced, and super-reduced rates, plus equivalence surcharges'). It distinguishes itself from siblings by focusing specifically on VAT rates rather than deductions, calendars, brackets, or other tax-related data.

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 provides explicit guidance on when to use alternatives: 'Use territory='canarias' for IGIC or territory='ceuta_melilla' for IPSI.' This clearly indicates that this tool is for Spanish VAT rates, with specific territory parameters for different tax systems, helping the agent choose correctly among sibling tools that handle different tax types.

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