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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds meaningful behavior: it returns the set of supported country storefronts and those values are meant to be reused as scoping keys for other tools, which is not derivable from the annotations alone.

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 sentences, zero waste. The purpose is front-loaded and the second sentence carries actionable chaining guidance rather than filler.

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?

An output schema exists, so return values need not be described. For a 0-parameter read-only listing tool, the definition covers purpose, safety, and downstream usage adequately; only a note on whether an argument (e.g., country filter) is ever required 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?

With zero parameters, the baseline is 4; there is nothing for the description to disambiguate. The description does not need to explain parameters and correctly does not attempt to.

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 ('List') and resource ('Zalando country storefront markets supported by the catalog'), making it immediately distinguishable from siblings like zalando_search or zalando_categories. An agent can tell it is the storefront/market enumeration entry point 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?

Explicitly tells the agent to feed a returned market into zalando_search, zalando_categories, or zalando_product to keep discovery scoped. This gives clear usage context and names the downstream alternatives, though it does not state when NOT to call it (e.g., vs. zalando_suggest).

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