add_tester_to_beta_group

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

Annotations already declare destructiveHint=true, idempotentHint=false and openWorldHint=true, so the 'MUTATES' emphasis is largely redundant with structured data. The description does add useful scope ('TestFlight access' and the existing-tester precondition) but says nothing about whether duplicate adds fail, whether testers get notified, or what permissions are required.

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?

A single sentence with the mutation warning front-loaded, followed immediately by the action and target. No filler, no restatement of the tool name.

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 two-required-parameter mutation with no output schema, the essentials (what changes, which entities are involved, that it is a mutation) are present and annotations cover the safety profile. What is missing is failure behavior on duplicates and the prerequisite that the tester already exists in the account, which matters for correct invocation.

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% and neither parameter has a description, so the description must carry the load; it does so only minimally by naming the two entities (tester, beta group) that map to testerId and groupId. It adds no format, source-of-id, or cross-argument constraint information beyond the property names.

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: add an existing tester to a beta group, and prefixes it with the domain scope (TestFlight access). The word 'existing' implicitly distinguishes it from create_beta_tester, but no sibling is named explicitly, keeping it just short of a 5.

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?

The phrase 'an existing tester' implies the precondition that the tester must already exist (i.e., use create_beta_tester first otherwise), but this is inference rather than explicit guidance. There is no statement of when to prefer add_build_to_beta_group or how to handle a tester that isn't yet registered.

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