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

While readOnlyHint already signals the read-only nature, the description goes further by disclosing the exact return shape (HAL collection embedding fx:coupons) and the underlying HTTP endpoint. This gives an agent expectations about the response format without an output schema. It does not detail pagination behavior, but the readOnlyHint combined with response details covers the key behavioral characteristics.

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 concise sentences lead with the purpose, then provide response format and endpoint. There is no filler, and the most decision-relevant information is front-loaded.

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 read-only list operation with fully documented parameters and no output schema, the description is complete. It names the resource, scope, response container (HAL + fx:coupons), and the HTTP endpoint, so an agent has everything required to invoke and interpret the result. The lack of a separate output schema is mitigated by the response format hint.

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 description coverage is 100%, with all four parameters fully documented in their property descriptions. The tool description adds no parameter-level semantics beyond the schema. Baseline 3 applies because the schema already does the heavy lifting.

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 opens with a specific verb and resource, 'List a store's coupons', and clarifies that coupons mean discount codes and their rules. This separates it from sibling list tools (carts, customers, items, subscriptions, transactions) purely by resource. No ambiguity about what operation this performs.

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?

The tool's scope is clearly contextualized as reading a store's coupons, which is sufficient because no same-resource sibling exists. It does not explicitly name alternatives or exclusion conditions, but it is obvious from the resource-oriented description when this list tool is appropriate.

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