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

Annotations already declare destructiveHint=true, idempotentHint=false and openWorldHint=true; the description adds real value beyond them by emphasizing 'This SENDS AN EMAIL TO THE CUSTOMER each time it is called,' which concretely explains the non-idempotent, externally-visible side effect and warns against repeated invocation. It does not cover rate limits or whether the link expires, which keeps it below 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?

The 'WRITE:' prefix front-loads the mutation nature, the irreversible/outbound warning follows immediately, and the guardrail conditions come next. Three tight sentences plus the endpoint path, with no 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?

For a 3-parameter mutation with no output schema, the description covers action, side effect, trigger conditions, and the confirmation requirement — everything an agent needs to decide and call correctly.

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% and each parameter already has a clear description, including the const-true confirm_send gate. The description's 'confirm_send must be true' largely restates schema content rather than adding format or source-of-value guidance, so the baseline 3 is appropriate.

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 description opens with a specific verb+resource: 'make Shopify email the customer a link to update their payment method for this subscription.' It distinguishes itself from all read-side siblings (get_customer_payment_methods, get_subscription) by making clear it sends an outbound email rather than retrieving data.

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 states explicit trigger conditions ('failed payments or expired cards') and a hard guardrail ('only when the user asks, and confirm_send must be true'). It does not name an alternative sibling for the common adjacent use case (e.g. checking payment methods first via awtomic_get_customer_payment_methods), so it stops short of full routing guidance.

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