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

With no annotations, the description carries the burden of behavioral disclosure. It usefully reveals that the tool requires an authenticated Proof account and that it is meant to be polled repeatedly. However, it does not describe what terminal states look like, what the response contains, or what happens with an invalid session ID.

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 description is compact and front-loaded: the purpose appears in the first sentence, followed by a needed access note. The parenthetical '(Claude Code: /mcp → Authenticate)' is somewhat environment-specific, but it does not make the description bloated.

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 simple one-parameter tool, this is close to sufficient: it explains what to call, with what key, and the authentication prerequisite. The main gap is the absence of return-value or terminal-state details, which matters because there is no output schema to fill that gap.

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?

The only parameter, session_id, is already fully described in the schema ('Add-phone session ID'), so schema coverage is 100%. The description's 'by session ID' simply restates the parameter and adds no extra meaning about format, origin, or lifecycle.

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 first sentence states a specific verb ('Check'), the resource ('status of an in-progress phone addition'), and the lookup key ('by session ID'). This makes the tool's purpose unambiguous and clearly separates it from sibling tools like start_add_phone or get_add_email_status.

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 description provides clear operating context: it is a polling tool ('Poll until terminal state') and it explicitly warns that authentication is required, including how to authenticate or sign in via start_login. It does not explicitly name alternatives or when-not-to-use conditions, but the invocation context is clear enough.

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