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

Annotations already declare readOnlyHint=false, destructiveHint=false and idempotentHint=false; the description reinforces this with the "WRITE:" prefix and the add-only framing ("It only adds a group"), which tells the agent nothing existing is mutated or removed. It stops short of stating whether a duplicate name is rejected or what gets returned.

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 short sentences, front-loaded with the WRITE marker and the core action, then the scoping clause and endpoint. No filler.

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 4-parameter additive creation tool with full annotation coverage and no output schema, the description covers what is created, that it is additive, and where it lives. The main residual gap is that it says nothing about the created group identifier or how initial coupon capacity works, which matters if the caller needs the new group's id for follow-up calls.

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%, so uuid, name, active and coupons are all documented with type and length constraints in the schema itself. The description only restates that the group belongs to a campaign and may include initial codes, adding no format or default detail beyond that (the default-true for `active` lives in the schema).

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 and resource ("create a coupon group for a campaign") plus the optional nested resource ("first coupon codes"), and scopes it with "It only adds a group." It never names a sibling such as referralhero_add_coupons or referralhero_get_coupon_group, so differentiation is implied rather than explicit.

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 only adds a group" hints at an exclusion (adding codes to an existing group belongs elsewhere) and the endpoint anchors it to campaigns, but no alternative tool is named and no precondition is stated. Usage is inferable but not spelled out.

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