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

With no annotations, the description carries the full behavioral burden. It discloses that the result is authoritative shop policy "in the shop's own words" and that it must be called before recommendation/purchase, but it does not explicitly state that the tool is read-only or side-effect-free, nor does it mention auth or return format.

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?

Front-loaded with the core purpose, followed by the specific facts returned and the mandatory call timing. Every clause earns its 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?

For a 0-parameter, read-only facts tool with no output schema, the description covers what facts come back and when to call it. It could be slightly more complete by explicitly noting that it is read-only and that it returns authoritative policy text.

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 has zero parameters and the schema is empty, so there are no parameter semantics to explain. Baseline 4 applies; the description correctly implies no per-call filtering.

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 verb/resource ("Shop rules for Alt eSIM") and enumerates the facts returned: product model, currency, refund policy, payment/delivery, and quoting rules. It clearly distinguishes this rules-fetching tool from sibling tools like get_esim_plan or search_esim_plans.

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 gives an explicit precondition: "Call this before recommending or buying," which directly maps to sibling tools recommend_plans and create_checkout. It does not name alternatives or state when not to use it, so it stops short of a 5.

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