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

Annotations already cover the read-only, non-destructive, idempotent safety profile. The description adds meaningful behavior beyond those annotations: exact-match semantics, batching across up to 10 IDs, and the explicit failure behavior that unknown IDs appear in not_found rather than being guessed.

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?

Three tightly-written sentences deliver the trigger condition, ID format, exclusion, alternative, and failure behavior with no filler. The most decision-relevant information is front-loaded.

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 single-parameter read-only lookup with an output schema, the description covers when to use it, what the input looks like, the limit, the sibling to prefer for fuzzy cases, and how unknown IDs are handled. Nothing critical is missing for an agent to invoke it correctly.

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%, so the ids parameter is already documented. The description adds valuable semantics beyond the schema by specifying the expected ID format ('brand:starbucks') and clarifying that exact brand slugs are acceptable, which directly helps the agent construct valid input.

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 a clear action ('look up'), a specific resource ('CardDeals product IDs or brand slugs'), and the batching scope ('up to 10 ... to compare in one call'). It also differentiates itself from search_gift_card_deals, and the title signals the multi-item contrast with get_gift_card_deals.

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 explicitly says when to use the tool ('when the user supplies up to 10 exact... IDs or slugs') and when not to use it ('Do not use it for fuzzy discovery'), naming the alternative (search_gift_card_deals). This leaves little room for an agent to route incorrectly.

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