update_subscription

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

Annotations already flag destructiveHint=true, idempotentHint=false, and openWorldHint=true, so the safety profile is partly covered. But the description adds nothing: it does not say that the change affects a live App Store subscription, that omitted fields are left untouched, that the operation is not idempotent, or that App Review-relevant fields are in scope. For a destructive mutation with no output schema, this is a substantial gap.

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 single sentence is front-loaded and free of waste, but it is under-specified rather than concise in a useful way – brevity here costs information rather than saving it.

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 five-parameter destructive mutation with no output schema and no annotations that explain side effects, the description should say what changes, what is preserved, and what the result looks like. None of that is present, leaving the agent dependent entirely on the schema field names.

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%, with each of the five parameters documented in the schema itself (including the required subscriptionId and the meaning of groupLevel priority). The description contributes no additional parameter meaning, so the baseline 3 applies.

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 names a specific verb (Update) and resource (subscription), so the basic operation is unambiguous. However, it adds nothing beyond the tool name and does not distinguish it from the many sibling mutation tools (update_iap, update_beta_group, update_app_description), nor does it say which aspects of the subscription are updatable.

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 when-to-use guidance, no prerequisites, and no mention of alternatives such as create_subscription or set_subscription_price. The agent must infer from the name alone that this is the tool for modifying an existing subscription's metadata.

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