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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuine value by disclosing the returned payload ('code, available, sent_at') and the underlying endpoint, but says nothing about auth, failure modes, or pagination of the embedded coupon list.

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 tight sentences with the returned fields front-loaded before the endpoint reference. No filler, though the 'GET /lists/...' fragment is developer-oriented rather than agent-oriented.

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 no output schema, the description's enumeration of returned coupon fields is the main source of return-shape information and it delivers that. For a simple two-param read tool this is close to sufficient; only the size/ordering of the embedded coupon list is left unspecified.

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 coverage is 100%: both uuid and coupon_group_id carry rich descriptions referencing the campaign and coupon-group listing tools. The description adds no parameter detail beyond echoing the endpoint path, so baseline 3 is appropriate.

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 clear verb+resource ('Get' + 'coupon group') and immediately signals scope by noting it returns one group with all its coupons, which implicitly contrasts with the plural list tool. It stops short of naming the sibling 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?

The singular 'One coupon group' implies this is the single-record fetch versus referralhero_list_coupon_groups, and the schema description points to that list tool. But the description never states when to choose this tool or what happens if the id doesn't exist.

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