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

With no annotations, the description carries the full behavioral burden. It usefully discloses the 100-item cap and the authoritative EOS source, but says nothing about authentication, rate limits, partial-failure behavior, or how invalid EORIs are handled. Return values are covered by the output schema, so that gap is excused.

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 that states the action, the limit, and the data source with no wasted words. Ideal density for a one-parameter tool.

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-parameter batch verifier with an output schema, the description covers the essentials an agent needs: what is verified, the batch cap, and the source of truth. Only the failure/invalid-number semantics are absent, a minor gap given the low complexity.

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% for the single 'eoris' array parameter, so the description must compensate. 'up to 100 EU EORI numbers' clarifies both the element type (EORI numbers) and a maximum batch size the schema does not enforce via maxItems, adding real information beyond the schema.

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 a specific verb (Verify), resource (EU EORI numbers), batch scope (up to 100 at once), and data source (official EOS). It implicitly distinguishes itself from the single-record verify_eori via 'batch'/'at once', but never names a sibling explicitly, leaving the batch-vs-single and EORI-vs-VAT routing to inference.

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?

Batch context is implied by 'up to 100 ... at once', so an agent can infer this is for multi-number checks. However, there is no explicit statement of when to prefer this over verify_eori or the generic verify_batch, and no exclusions or prerequisites are given.

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