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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety and world-access profile is covered. The description adds nothing beyond that—no note on what a miss returns (null vs error) or how the two code types resolve to one promotion.

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 compact sentence that front-loads the resource and the lookup key. Nothing is wasted, though it is terse enough that a little more routing context could have been added without bloat.

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?

An output schema exists, so return-value detail is not required in the description. For a simple two-parameter read lookup, this covers what an agent needs, with only minor gaps around miss behavior and sibling routing.

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%, and the schema itself documents both parameters and the 'exactly one of' constraint. The description only restates 'redemption code or serialized code' without adding syntax or format detail, so the baseline 3 applies.

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?

States a specific verb (lookup) and resource (a single KFC promotion), and the singular form distinguishes it from the plural sibling kfc_promotions. It does not explicitly name the alternative, but the single-vs-list contrast is clear from the name and description.

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 phrase 'looked up by its redemption code or serialized code' implies the lookup scenario, and the code-based input signals when this tool is appropriate. However, there is no explicit when-to-use or when-not guidance, nor a pointer to kfc_promotions for browsing without a code.

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