get_invoice_requirements

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

Annotations already declare read-only and idempotent. Description adds value by specifying the output structure ({country, mandatory_fields, optional_fields, notes}) and the data source (EU VAT Directive and local implementations). No contradictions.

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?

Three sentences, each serving a distinct purpose: purpose, output shape, usage guidance. No fluff, front-loaded, and efficiently structured.

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 simplicity (1 param, output schema exists), the description is complete enough. It mentions the return shape and usage context. Slight deduction because actual output schema details are not shown, but description covers key aspects.

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 a well-described parameter (country_code with example values). Description does not add extra meaning beyond the schema, but given high coverage, a baseline of 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 the tool returns mandatory fields for a valid VAT invoice for a European country, using specific verb 'Returns' and resource 'mandatory fields'. It distinguishes from siblings like 'validate_invoice_schema' and 'get_vat_rate' by focusing on invoice requirements.

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?

Explicitly says when to use: generating invoices, validating templates, compliance checks. Also includes a disclaimer about not being legal advice. Lacks explicit when-not-to-use or alternatives, but context is clear.

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