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

Annotations already declare readOnly, idempotent, and non-destructive behavior; the description adds the cardinality range (two to eight) and accepted identifier types. It does not mention failure behavior, invalid identifiers, or how results are presented, but the output schema mitigates return-value concerns.

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 sentence with an active verb and essential scope constraints in parentheses. No filler, no repetition of annotation or schema data.

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?

Annotations and output schema cover safety and result shape, and the core invocation (gtins) is clear. However, the two optional parameters are undocumented in both the schema and the description, leaving ambiguity about locale and decision context.

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 compensate; it explains gtins as GTINs or catalogue ids with a 2–8 count, but says nothing about market or decision_id. An agent cannot tell what these optional parameters mean or when to populate them.

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 action (compare), a clear resource (products, variants, shades), and a distinctive scope (side-by-side, two to eight GTINs or catalogue ids). This differentiates it from sibling single-item lookups like get_item or verify_gtin.

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?

No explicit when-to-use or when-not-to-use guidance is provided, and no alternative tools are named. The reader must infer from the sibling list that this is for multi-item comparison rather than single-item retrieval.

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