mhlb_get_coupon

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

Annotations already declare readOnlyHint=true and openWorldHint=true, covering safety and the possibility of a null/empty result. The description adds the detail that the coupon is 'currently applied to the account' and includes 'if any', which aligns with openWorldHint but doesn't introduce new behavioral context (e.g., auth requirements, rate limits, or response format). Since annotations carry most of the burden here and the description adds minimal extra value, a 3 is appropriate.

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 description is a single, efficient sentence that leads with the action and resource, and includes the qualifier 'if any' to set expectations. There is no filler or redundancy; every word contributes to the meaning, making it appropriately concise and well-structured.

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 openWorldHint and readOnlyHint annotations, the description is nearly complete. It states what the tool does and hints at the possible empty result via 'if any'. The absence of an output schema means the exact return shape is not specified, but given the simplicity and the annotations, the description is sufficient for an agent to invoke the tool correctly. A 5 would require explicit mention of the return structure or edge cases, but this is adequate given the context.

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, so the baseline is 4 per the rubric. There is nothing for the description to clarify about parameters, and the schema (which is empty) provides no further information. The description adds no parameter-related details because none are needed.

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 states a specific verb ('Get') and a specific resource ('the coupon currently applied to the account'). It clearly distinguishes this from sibling tools like mhlb_apply_coupon and mhlb_remove_coupon by focusing on reading the current state. The phrasing 'if any' also clarifies the possibility of no coupon being applied, leaving no ambiguity about the tool's purpose.

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 description does not explicitly mention when to use this tool versus alternatives like mhlb_apply_coupon or mhlb_remove_coupon. However, the getter nature is implied by the name and the readOnlyHint annotation, and the sibling list makes the read-vs-mutate distinction obvious. It provides clear context that this is for inspecting the current coupon, but it stops short of explicitly guiding the agent on when to call it instead of others, which would merit a 4.

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