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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds real domain context beyond annotations: prices come from Stripe in haléře, the vendor is not a VAT payer so prices are final, and the 30-day free trial with first charge on day 31. It does not say whether the plan list is static or region-dependent, but the added pricing semantics are substantial.

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 purpose is front-loaded in the first clause, and the follow-on sentences about currency units, VAT and the trial period each carry information an agent may need to relay to a user. It is dense but not padded; the trial/payment paragraph is arguably commercial detail that could be trimmed for a pure listing tool.

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 an output schema present and no input parameters, the description only needed to frame the resource and any non-obvious semantics of the returned data; it does both, covering plan tiers, price units, tax treatment and the trial-charging behaviour. Nothing required to call 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. The description correctly spends no text on inputs and instead explains the semantics of the returned price values (haléře, final prices including VAT treatment).

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 opening clause states a specific verb and resource: it returns the tariffs/plans that can be set up via MCP, and specifies whether each is free or paid with monthly and yearly pricing. No sibling tool (check_subdomain, create_store, docs, store_creation_status) overlaps with plan listing, so an agent can route unambiguously.

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 only implied: because it returns plans 'that can be set up via MCP', an agent can infer it should be called before shopzi_create_store to learn pricing. There is no explicit statement of when to call it, no mention of prerequisites, and no reference to any sibling as an alternative or follow-up.

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