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

With no annotations, the description carries the full burden of disclosing behavior. It adds the useful behavioral trait that the tool operates offline, and it indicates its core functionality. However, it does not disclose whether the tool validates or merely computes, nor any edge cases or error behavior.

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 a single compact line that front-loads the essential information: the domain (Barcode/EAN), the specific operations (check digit and GS1 prefix), and a key behavioral trait (offline). There is no filler or redundant phrasing.

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?

Despite the tool's apparent simplicity and the presence of an output schema, the description leaves a critical gap: it never defines the 'q' parameter, and it offers no guidance on when to select this tool over closely related siblings. The offline label helps, but the overall context is insufficient for confident, correct invocation.

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?

The schema has one parameter 'q' with zero description coverage, and the tool description does not explain what value q should contain or its expected format. The tool name and description make it inferable that q is likely the EAN/UPC string, but this is not explicitly stated, leaving room for ambiguity.

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 that the tool handles EAN/UPC check digits and GS1 country prefixes, which conveys a clear function and distinguishes it from generic barcode or checksum siblings. It lacks an explicit verb like 'validate' or 'compute,' but the noun phrase makes the intended purpose reasonably evident.

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 provides no explicit guidance on when to use this tool versus alternatives such as barcode, checksum, or luhn. The only contextual hint is 'offline,' which distinguishes it from network-dependent tools but does not explain selection criteria or exclusions.

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