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

readOnlyHint=true is consistent with a status-check tool, and the description adds behavior the annotation does not: this is a polling endpoint that should be called repeatedly until a terminal state, and it requires an authenticated Proof session (possibly created by start_login). It stops short of naming the terminal states or rejection behavior, so not a 5.

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?

Purpose is front-loaded in the first sentence, followed by polling and auth guidance. The paragraph about making sure the link/SMS appears in reply text is a little verbose and tangential to tool selection, but it does carry task-relevant guidance rather than filler.

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, the description should say more about what a status response contains and which states count as terminal (e.g. complete, expired, failed). Authentication and polling behavior are covered, but the return-side picture is left entirely to inference.

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% and the single session_id parameter is already documented in the schema as the add-phone session ID. The description repeats 'by session ID' without adding format, provenance, or lifecycle detail, 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?

States a specific verb and resource ('Check the status of an in-progress phone addition') plus the input key ('by session ID'). It is readily distinguishable from start_add_phone and from the sibling get_add_email_status, so an agent can pick it 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 guidance ('Poll until terminal state') and spells out the authentication path — authenticate the client, or sign in via start_login since that session opens this tool, then retry. It lacks an explicit 'do not use for X' exclusion, but the context is otherwise unambiguous.

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