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

Annotations already flag destructiveHint=true and idempotentHint=true, but the description adds crucial context: unknown emails may be created as marketing contacts, and subscription can trigger campaigns or automations. It also states the reply carries per-person outcomes and cites the underlying POST endpoint, which is more than the annotations provide.

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?

One front-loaded paragraph beginning with 'WRITE:', every sentence adding distinct value: action, scope, side effects, consent gate, return format, endpoint. No repetition or 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?

Given a single parameter object, no output schema, and destructive/idempotent annotations, the description covers the behavioral risk, side effects (contact creation, campaign triggering), consent requirements, and return shape. An agent has everything needed to call it safely.

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?

With schema description coverage at 0%, the description must compensate. It clarifies that subscribers are identified by email and that audiences are numeric ids from SuiteDash > Marketing, which adds useful meaning. However, it does not document the optional first_name/last_name fields or the 50-item batch limits, leaving part of the schema unexplained.

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 and resource: 'subscribe people (by email) to one or more marketing audiences'. It also scopes the resource precisely ('numeric audience ids from SuiteDash > Marketing'). No sibling tool does marketing subscription, so it is clearly differentiable.

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 gives explicit when-and-when-not guidance: only for people who have consented, and only when the user explicitly asked. That is a strong usage gate for a write that enrolls real people into campaigns.

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