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

Annotations already declare destructiveHint=true and openWorldHint=true, so the safety profile is known; the description goes further by stating exactly what happens ('the user's phone is called right away'), that it is not a preview, and that the side effect is a real outbound call to a human. The prohibition on passing the receptionist number also discloses a concrete failure mode (forwarding loops).

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?

Five short sentences, front-loaded with the action and then the risk warning and confirmation requirement. The 'never pass the receptionist number' warning appears twice (description and schema description), which is mild but deliberate redundancy rather than wasted text.

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?

Covers what the call does, that it is destructive and live, and the human-in-the-loop requirement — everything needed to invoke it safely. The one remaining gap is outcome: there is no output schema and the description never says what the agent receives back or how to interpret a successful versus failed verification.

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 schema already documents the single optional parameter, its null default, and the receptionist-number prohibition. The description only repeats that guardrail rather than adding syntax, formatting, or validation 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 — places an automated call to the user's regular number and verifies forwarding to the receptionist — plus an explicit scope limiter ('This tests forwarding only'). It does not name the closest sibling (getCarrierForwardingInfo) or any other alternative, so differentiation is by scope rather than by routing.

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 a hard exclusion ('Never pass the SkipCalls receptionist number as the target') and a stated prerequisite workflow: show the exact change and get explicit user confirmation immediately before calling. It does not point to a preferred sibling when the user only wants to inspect forwarding status, so the agent must infer that boundary.

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