Send a customer a sign-in link. Money is integer minor units (cents). Calling this changes nothing: it returns a preview of what would change and a confirmation link. Only the merchant, on that page, can make it happen.
| Name | Required | Description | Default |
|---|---|---|---|
| Yes | The customer's email, as on their file. Shoppers have no password; this sends the link that signs them in. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Goes well beyond the annotations by disclosing that calling it mutates nothing, returns a preview plus a confirmation link, and requires the merchant to act on a page before anything happens - genuinely useful context for a 'reset' tool. The stray 'Money is integer minor units (cents)' sentence is irrelevant to this tool and adds noise, keeping it from 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?
Mostly tight and front-loaded, but the second sentence about money being in integer minor units is entirely off-topic for a one-email-parameter tool, wasting space and risking confusion. Removing it would sharpen the definition considerably.
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 single-parameter tool with no output schema, the description covers the important behavior (preview, confirmation link, merchant gate) adequately. The remaining gaps are the absence of when-to-use guidance and the irrelevant money sentence.
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 'email' parameter is fully documented in the schema, so baseline is 3. The description adds only the contextual note that shoppers have no password and this link signs them in, which is helpful framing but not new parameter syntax.
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 states a concrete verb+resource ('Send a customer a sign-in link') and reconciles the misleading name by noting shoppers have no password. However, it never contrasts the tool with close siblings like customers_message, customers_note, or customers_change_email, so an agent gets no help distinguishing it from the other customer-contact tools.
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 explains what the tool does mechanically but gives no guidance on when to prefer it over alternatives, and names no sibling. A reader is left to infer the use case from 'this sends the link that signs them in.'
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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