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

With annotations present (readOnlyHint=false, destructiveHint=false, idempotentHint=false) the bar is lower, and the description still adds meaningful behavior: a dry-run preview and a merchant-gated confirmation step. The one tension is that 'Calling this changes nothing' sits awkwardly against readOnlyHint=false, though the preview-link mechanism explains the non-read-only classification.

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 core sentences are front-loaded and efficient, but 'Money is integer minor units (cents)' is boilerplate carried over from a payment tool and has no bearing on this tool, diluting an otherwise tight description.

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-parameter tool with no output schema or annotations on returns, the description supplies the essential missing piece: the call produces a preview and a confirmation link rather than an immediate change. Only the stray money sentence and the unstated reason for readOnlyHint=false keep it from being fully complete.

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 100%, so both parameters are already documented (including the 'past orders keep the address they were placed with' nuance). The description adds nothing about email/newEmail, and its one numeric remark concerns money units, which is irrelevant here. 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?

The opening sentence names a specific verb and resource ('Move a customer to another email'), and the preview/confirmation detail implicitly separates it from customers_create, customers_lookup, or customers_delete. It stops short of explicitly naming a sibling or scope boundary, so it is clear but not fully differentiated.

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?

It gives strong call-context: invoking it changes nothing immediately, it returns a preview plus a confirmation link, and only the merchant can complete the change on that page. That effectively tells the agent when to call it (to initiate, not to commit) without naming alternatives.

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