ASC Append Subscription Disclosure

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

Annotations cover safety flags (destructiveHint, idempotentHint, openWorldHint), but the description adds context beyond them: it is a live write requiring human approval, idempotency works by skipping when the marker is present, output is truncated to 4000 characters, and it can return an approval_required refusal. That approval workflow and truncation constraint are genuinely new information for the caller.

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-loads the action, then uses compact labeled clauses ('Use when:', 'Not for:', 'Returns:') that each carry distinct information. No sentence is redundant or padding.

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?

With an output schema present, return values need no expansion, yet the description still summarizes them. Combined with annotations and full schema coverage, an agent has everything needed: trigger, exclusion, write/approval behavior, idempotency, and truncation limit.

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%, so bundle_id, terms_url, approval_id, privacy_url and disclosure_by_locale are already fully documented in the schema. The description alludes to the approval_id round-trip via the 'approval_required refusal' mention but adds no syntax or format detail beyond the schema, so the baseline of 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?

States a specific verb (append) and resource (subscription disclosure, Terms/EULA and Privacy links to the app description, in every language) with the Apple 3.1.2 rationale. It also explicitly names the sibling it is not (deliver_metadata), so an agent can separate it from other metadata tools without opening a 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?

Provides an explicit 'Use when: preparing a subscription app for review' trigger and a 'Not for: uploading other metadata (use deliver_metadata)' exclusion with a named alternative. Nothing about when to select this versus siblings is left to inference.

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