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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds that records are sourced with an official source_url and a checked date, which is meaningful trust context, but it says nothing about freshness policy, ordering, or behavior for countries with no mandate.

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 what the tool returns and followed by parameter guidance; every clause carries information an agent needs and nothing is redundant.

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 single optional parameter with an output schema and read-only annotations, the description covers format, default behavior, and the shape of each record. Minor gaps remain around error handling for invalid country values and result ordering.

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 0%, so the description must carry the parameter — and it does, specifying accepted forms (two-letter code such as 'be', 'de', 'ae', or a country name) and that omitting it returns all countries. It stops short of covering case sensitivity or unknown-country behavior.

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 names the specific resource (e-invoicing mandate dates) and its granularity (per country or all countries), plus the payload each record carries (source_url and check date). It does not explicitly distinguish itself from siblings like foreign_supplier_scope, but the purpose is unmistakable.

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?

'Leave it out for all countries' gives clear guidance on the no-argument case, but there is no statement of when to reach for this tool versus the related scope/provider tools, and no exclusions or prerequisites are mentioned.

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