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

Annotations only declare readOnlyHint=false, so the description carries most of the load, and it does add real behavior: opt-outs originate from the footer link, mAYL_send then suppresses pixel and link-wrapping automatically, and scope is owner-limited. It omits what happens when 'check'/'optin' targets an unknown or non-owned recipient, and whether 'optin' is idempotent.

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?

Front-loaded with the purpose, then the action semantics, then the downstream effect on mAYL_send — the ordering matches how an agent reads. Slight redundancy with the schema's own enum descriptions keeps it from a 5.

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 2-parameter tool with full schema coverage and no output schema, the description supplies the missing behavioral context (opt-out origin, send-time effect, ownership scoping). It could still say what 'list' returns and whether 'optin' confirms or errors, but nothing essential to calling it correctly is absent.

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 both 'action' and 'recipient' are already documented, including the enum meanings and the 'required for check/optin' rule. The description restates those semantics rather than adding format or edge-case detail, which is the baseline 3 case.

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?

Names a specific verb and resource ('Manage recipient tracking opt-outs') and enumerates the three discrete actions with what each does. It also distinguishes the tool from the send path by explaining that mAYL_send consumes this state, so an agent can place it relative to siblings without opening a schema.

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?

Each action value is paired with the situation that selects it ('list' for the whole opt-out set, 'check' for one recipient, 'optin' to re-enable), which effectively tells the agent when to use which mode. It stops short of explicit exclusions or prerequisites (e.g. permission level needed to run 'optin' for another owner's recipient).

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