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

Goes well beyond annotations by disclosing the affiliate source, a 3-hour refresh cadence, exclusions (never newsletters/emails, never risk-list shops), explicit null semantics for discount (never a guess), date-range interpretation (a date = the whole day), commission disclosure with ranking independence, and image sourcing rules. Annotations already cover read-only/idempotent safety, but the description adds rich operational context.

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?

Reasonably sized for a complex listing tool with no output schema, and the purpose is front-loaded. However, the field enumeration is a dense, semicolon-heavy run-on that is harder to parse than it needs to be, though most sentences earn their place.

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 the full burden and does so thoroughly: it describes every returned field (shop, type, title, discount, up_to, min_order, valid dates, url, image, image_source, fetched_at) and the ordering rule. Nothing an agent needs to call or interpret the tool 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 50% (country documented there, limit not). The description adds meaning for country (one country, the shop's country) but does not explain the limit parameter, how many rows it caps, or pagination behavior. Baseline 3 is appropriate given the schema handles the other half.

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 and resource (coupon codes and promotions), scopes it to compared shops and today, and names the data source (eHUB). It is clearly distinguishable from siblings like daily_deals and find_best_price, the latter being explicitly named as a follow-up.

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?

Gives concrete context: one country (the shop's country), soonest ending first, and directs the agent to find_best_price with a product name for price comparison. It does not explicitly say when not to use this versus daily_deals or list_shops, but the usage context is otherwise clear.

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