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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior. The description adds useful behavioral nuance by stating that non-existent catalog names are returned as useful information rather than an error. This goes beyond the annotations without contradicting them.

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 two sentences with the core behavior front-loaded. The second sentence adds a valuable, non-obvious output detail without redundancy or filler.

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?

This is a simple one-parameter tool with a rich output schema and strong annotations. The description covers the comparison semantics, the required minimum input, and the notable behavior around unknown names, leaving no critical operational gap.

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 for the only parameter is 0%, so the description must compensate. It clarifies that 'names' refers to plan names and implies at least two are needed ('dos o más planes'). It does not address details like duplicate names or exact matching, but it provides the essential meaning.

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 uses a specific verb ('compara'), a clear resource ('planes'), and a concrete method ('por nombre, uno al lado del otro'). This clearly distinguishes it from sibling tools like get_product or search_products, which do not imply side-by-side comparison.

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?

When to use the tool is implied by the comparison verb, but no alternatives are explicitly mentioned and there is no when-not-to-use guidance. It is only inferred that you should use this when comparing two or more plans.

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