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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real behavioral context beyond them: results are "live" (valid now, not expired) and "newest" (recency-oriented), which tells the agent what kind of inventory it receives. It stops short of stating sort order or whether expired codes ever appear.

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?

Two short sentences, zero redundancy, with the core capability front-loaded before the usage hint. Every clause carries information the schema does not.

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?

For a simple two-parameter read tool with full schema coverage and annotations, this is close to sufficient. The remaining gap is that with no output schema, nothing describes the return shape (e.g., what fields a code record contains or whether results are ordered by recency), which the "newest" claim implicitly promises.

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 100%, so both limit and category are fully documented in the schema, making 3 the baseline. The description only adds that category is optional and that there is no store filter ("across every store"), which is a marginal gain over the enum and integer bounds already present.

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 newest live codes across every store, optionally within one category" gives a specific resource (promo codes) plus a scope qualifier (newest, live, all stores) and an optional filter. It is clear on its own, but it never names or contrasts with the obvious sibling find_promo_codes, so the agent gets no explicit differentiation.

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?

"Good for 'any new deals on…' questions" supplies a genuine use case, which is more than nothing. However, there is no when-not guidance and no routing to find_promo_codes or search_stores, so the agent must infer the boundary between this discovery tool and the lookup siblings.

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