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

Beyond the readOnlyHint annotation, the description discloses that the tool is deterministic, requires no account, and returns the validity status, normalized GTIN-14, and exact error on failure. This gives the agent a strong model of what to expect without needing to invoke the tool.

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 efficient: three sentences, with the main purpose front-loaded and supporting behavior placed at the end. Some parenthetical detail about Sunrise 2027 and DPP is informative but not strictly necessary, keeping it from a perfect score.

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?

The description covers the tool's inputs, outputs, and usage timing, which is strong given there is no output schema. It does not explicitly state what happens when both gtin and digital_link are provided or when neither is provided, which is a minor gap for a tool with zero required parameters.

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%, so the description adds no essential parameter meaning beyond what the schema already documents. It does clarify that only one identifier type (GTIN or Digital Link) is expected at a time, but the individual parameter descriptions already carry the semantic load.

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') and a clear resource scope (GTIN/EAN barcode numbers and GS1 Digital Link URLs). It also states the return value and error behavior, which makes the tool's purpose unambiguous and distinguishes it from sibling creation/DPP-readiness tools.

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 gives explicit guidance: use it before printing labels or QR codes to ensure GS1 conformance. It does not name alternative tools or state exclusions, but the context is clear enough for an agent to know when this validation step is appropriate.

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