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

Annotations already declare readOnlyHint=true and openWorldHint=false, and 'Read-only' merely restates that. The value added is the disclosure of the return payload (discount code, expiry date, both normal and discounted prices) and the word 'any', which hints at the possibility of no active offer — useful for a tool with no output schema.

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?

One sentence, front-loaded with the payoff (discount code) and packed with concrete detail — an example code, a percentage, and an expiry date. Nothing is wasted.

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 zero-parameter read tool with no output schema, the description covers the return shape well enough to call it blind. A minor gap: it doesn't say what is returned when no offer is active (empty result vs error).

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 the schema carries no semantics to explain and the baseline of 4 applies. The description correctly adds no parameter chatter and stays focused on output.

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 (Return) and enumerates the exact resources: active discount code, its expiry, and every paid pack's normal and discounted price. That content clearly separates it from list_packs or get_buy_link, though no sibling is named explicitly.

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 by the returned content — an agent can infer this is the pricing/discount lookup, but the description never says when to prefer it over list_packs, recommend_pack, or get_buy_link, nor any precondition such as needing a code before checkout.

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