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

Annotations already declare readOnly, non-destructive, open-world behavior. The description usefully adds that the tool reports partial failures rather than aborting, which is a real behavioral trait not in the annotations, but it says nothing about auth, rate limits, or how partial failures are surfaced.

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 tight sentence with the resource front-loaded and no filler. The trailing 'reporting partial failures' clause is slightly abrupt but still earns its place by conveying failure semantics.

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?

With no output schema, the description carries more burden but only covers scope and partial-failure behavior. It does not explain the response shape, the two collections returned, or that pagination applies per collection, leaving gaps for a 4-parameter tool.

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 75% and the schema already describes page, limit, and country. The description only implies the 'store' parameter via 'named merchant' and hints at per-collection paging through 'both...discounts and promotions' (matching limit's 'per collection' note), but adds no format or syntax beyond the schema.

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 clear verb ('Find') and resource ('product discounts and promotions at a named merchant'), and the merchant-scoping distinguishes it from broader siblings like search_deals or get_best_deals. It stops short of naming any sibling explicitly, so an agent must infer the boundary.

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?

There is no explicit when-to-use, when-not-to-use, or alternative routing. The agent can infer that this is the store-scoped lookup, but nothing tells it why to pick this over search_deals, find_promo_codes, or get_best_deals.

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