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

Annotations already declare read-only, idempotent, non-destructive behavior. The description adds useful context beyond that: it draws from a 47-country table and includes official sources, which tells the agent the answer is authoritative and reference-oriented.

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 definition is a single dense sentence with the core scope front-loaded. It is efficient, though the clause about returned contents is slightly packed in and could be clearer.

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 an output schema present, the description need not explain return structure, but it does summarize the included fields. The main remaining gap is a brief note on country-code normalization or error handling, but overall the definition is sufficient for a safe lookup call.

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 parameter meaning. It does by stating the country input accepts a two-letter code or an English name, which is essential for correct invocation. It does not describe invalid-input behavior, keeping it below a 5.

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 states a precise question-domain: whether a supplier with no establishment in a country must e-invoice there, plus the data returned (system, B2B status, foreign-supplier applicability). This is clearly distinguishable from siblings like deadlines or providers.

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 implied use case is clear from the tool title and description, but there is no explicit 'use this when' or comparison to sibling tools. An agent can infer it is a country-scoped lookup, but the routing guidance is only implicit.

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