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

Beyond annotations, the description discloses the external-email side effect, the consent_evidence requirement for Active status, the UTC offset constraint on collected_at, retry guidance, and required permissions. This adds substantial context that the annotations alone do not 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?

The description is three sentences long, each packed with relevant information: main purpose, constraints, side effect, retry guidance, permissions, and a link. It is front-loaded with the core action and contains 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?

The description covers the main purpose, scope exclusions, consent requirements, time constraints, external-email effect, retry strategy, permissions, and an API reference. With the output schema available to describe return values, the description is fully sufficient for an agent to correctly select and invoke the tool.

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 input schema provides descriptions for both parameters and the nested ConsentEvidence object, covering all fields at 100% coverage. The description's mention of collected_at constraints is also present in the schema, so it adds no new parameter-level information beyond what the schema already provides.

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 opens with 'Changes the delivery status for one Subscriber,' specifying the exact verb and resource. It further distinguishes itself from sibling tools by explicitly stating it does not change profile, targeting, or Sequence enrollment fields, making its purpose unambiguous.

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 phrase 'without changing profile, targeting, or Sequence enrollment fields' clearly implies this tool is for status-only updates, while 'Retry after reading the current resource state' gives a practical usage scenario. However, it does not explicitly name alternative tools like subscribers_update or subscribers_upsert, so it misses a clear when-not-to-use statement.

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