apple_create_subscription

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

With no annotations, the description carries the burden well: it flags the operation as an external/live action, warns that product_id is IMMUTABLE and non-reusable, and discloses the resulting MISSING_METADATA state plus what is still required. It does not discuss permissions, error behavior, or reversibility, which keeps it out of the top band.

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 purpose and the external-action warning, then grouped into three short paragraphs covering immutability, field semantics, and lifecycle state. Every sentence provides decision-relevant information with 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?

An output schema exists, so return-value explanation is unnecessary, and the description covers creation, field meaning, valid periods, and the required follow-up workflow. The only gaps are the unspecified locale parameter and group_id semantics, minor against an otherwise complete picture.

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 for the important fields: product_id's immutability/reuse constraint, the name vs display_name/description distinction, and the full subscription_period value set with the 'no installment plans' caveat. locale and group_id are left unexplained, which is why it is not a 5.

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 + resource + containment scope ('Create a subscription product inside a group'), which cleanly separates it from the sibling apple_create_subscription_group and apple_list_subscriptions. The 'External action' framing immediately signals a live-store mutation.

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?

Gives a real precondition ('check product_id against what the app sends before calling') and names the required follow-up tools (apple_set_subscription_price, apple_set_subscription_availability) to move the product out of MISSING_METADATA. It stops short of stating when NOT to use it versus a sibling group-creation tool, but the workflow context is clear.

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