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

Annotations already establish readOnly/idempotent/non-destructive, so the bar is lower; the description still adds real behavioral context the annotations cannot convey — the suggested_deals fallback when a brand has no coupons, and the distinct aliexpress response shape with min_spend and ends_at. It stops short of describing pagination or result ordering guarantees.

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 front-loaded definition and fallback behavior are efficient, but the definition then spends most of its length on a 22-item brand enumeration and an 8-category list. That coverage detail is mildly useful but reads as padding rather than decision-relevant content.

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 read-only, zero-required-parameter lookup with no output schema, the description covers scope, filters, fallback behavior, and one returned field (suggested_deals). Return shape and pagination remain unstated, but nothing needed to invoke it correctly is missing.

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%, so the baseline is 3, and the description adds genuine meaning beyond the schema: brand's optionality and its special 'aliexpress' semantics, and that category is only honored when no brand is supplied. The limit parameter is never mentioned in either place, leaving one small gap.

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 names a specific resource and its two variants ('verified, currently valid US coupons (type code)' and 'code-free promotions (type promotion)'), plus the geographic scope. An agent can distinguish this from search_deals and get_deal without opening the schema.

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?

It clearly states brand is optional and what happens without it (newest verified coupons, optionally category-filtered), plus the special 'aliexpress' path and the suggested_deals fallback. It routes to list_brands for the full list, but never contrasts itself with siblings like search_deals or get_deal, so the when-to-use guidance is clear but not exhaustive.

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