Create subscriber

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

Annotations already declare non-read-only, non-idempotent, open-world, non-destructive, so the safety profile is covered. The description adds a real behavioral consequence beyond annotations—that list_ids actually subscribes the new subscriber and that preconfirm bypasses double opt-in—but says nothing about duplicate-email handling, validation failures, or what is 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?

Three short sentences with no wasted words, and the core action is front-loaded. The style is telegraphic—parameter notes read as fragments rather than structured guidance—but nothing is padded.

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 6-parameter creation tool with no output schema, the description omits the return value (subscriber ID?), duplicate-email behavior, and the semantics of attribs/status. It covers only the two side-effect-related parameters, leaving an agent to guess at the rest.

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 0%, so the description must compensate, and it does explain the two least obvious parameters (list_ids and preconfirm) with meaning beyond the raw array/bool types. However, attribs (a free-form nested object), status (enum), and name are left entirely undocumented in both schema and description.

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 subscriber") that is unambiguous against siblings like subscriber_update or subscriber_get. It does not explicitly name an alternative, but the create semantics are clear enough that an agent can pick it without opening the 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?

There is no guidance on when to use this versus subscriber_update (e.g. upsert behavior) or subscribers_lists_change, and no prerequisites such as required permissions or what happens if the email already exists. The only usage hint is the implied side effect of list_ids.

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