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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description earns credit for genuinely non-obvious behavior: coupons are 'live' only, ordered best-first, and 'each coupon url reveals the code on the site' — telling the agent the discount code is not inline in the payload. It does not describe pagination or truncation behavior.

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 dense sentences, zero filler, and the core identity ('One shop by slug') is front-loaded before the payload enumerations and the code-reveal caveat. Every clause carries information.

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 must carry the return-value burden, and it does: it names coupons/offers, ordering, categories, and country variants. The minor gap is that it never clarifies what `limit` restricts, leaving the only tunable parameter's effect ambiguous.

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% and both parameters carry their own descriptions (slug sourcing, limit default 30 with a 50 cap), so the schema does the heavy lifting. The description reinforces the slug key but adds nothing about what `limit` bounds (coupons vs categories), so baseline 3 applies.

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?

It names the specific verb+resource ('One shop by slug') and enumerates the payload: live coupons and offers, categories, and the same shop on other countries' sites. This clearly separates it from list_coupons (aggregate feed) and search_shops (discovery), so an agent can pick it without opening a 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?

Usage is implied: a single-shop lookup keyed by a slug obtained from search_shops. However, the description never states when to prefer this over list_coupons or when the cross-country/category data matters, and gives no exclusions or prerequisites. Implied but not explicit.

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