Invite testers

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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is largely covered. The description adds the concrete auth prerequisite ASC_WRITE=1 and the external-vs-internal group constraint, which is useful, but the rerun-safety claim mostly restates idempotentHint and no return/pagination behavior is described.

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 core behavior well, but the rerun-safety idea is stated twice ('Safe to re-run with the same list' and 'Safe to re-run: steps already done are skipped'), which is redundant rather than additive. Structure is otherwise fine but the duplication costs 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?

With no output schema and full parameter coverage, the description carries the mutation warning (ASC_WRITE=1), idempotency, and group-type constraints, which is close to complete for a write tool. It could mention return/permission-error behavior but nothing critical for correct invocation is missing.

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 the baseline is 3, and the description adds meaning beyond it by explaining how the 'group' parameter behaves differently for external vs internal groups (email acceptance rules). The 'testers' dedupe/merge behavior ('added to the group instead of failing') also clarifies semantics not stated in the schema.

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 ('Adds testers to a beta group') plus the scope of the operation, which cleanly distinguishes it from siblings like create_beta_group, remove_testers and list_testers. An agent can identify the operation 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?

Gives clear operating context: external groups accept any email while internal groups only accept App Store Connect team users, and reruns are safe. It does not name an explicit alternative tool or an exclusion condition, but the group-type rule plus idempotency note gives strong selection context.

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