Letter IRL

Cancel scheduled mail

cancel_scheduled_mail

DestructiveIdempotent

Cancel a letter or postcard that was sent with an arrival date and is waiting for its mail date. Free until it goes to the printer: nothing is mailed, and what paid for it goes back to the account unless it expired or was refunded while the mail waited; the answer says what came back. Requires the orderId (from list_orders or the send) and confirm: true, after the person agrees, because it cannot be undone. Pay & Send orders and mail with no arrival date cannot be cancelled here.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "orderId": "<orderId>",
      "confirm": "<confirm>"
    },
    "name": "cancel_scheduled_mail"
  }
}

Input Schema

Name	Required	Description	Default
`confirm`	Yes	Set true once the person has agreed: a cancelled order cannot be restored
`orderId`	Yes	The orderId of the scheduled letter or postcard, from list_orders

Output Schema

Name	Required	Description
`status`	Yes
`message`	Yes
`orderId`	Yes
`returned`	Yes	What went back to the account
`alreadyCancelled`	Yes	True when it had already been cancelled: nothing changed now

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 7, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Annotations already flag destructiveHint and idempotentHint, but the description adds substantial context beyond them: it is free until printing, nothing is mailed, refunds return to the account except when expired or already refunded, and the response reports what came back. It also explains the irreversibility that motivates the confirm gate, which the annotations alone do not convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The scope and highest-risk constraint are front-loaded, and every clause carries information. The middle clause about refunds is dense and semicolon-chained, making it slightly harder to scan than it could be, but there is no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a destructive, irreversible mutation with an output schema, the description covers scope, exclusions, prerequisites, cost/refund behavior, and response content. The output schema handles return-value detail, so nothing material is missing for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description adds meaning: orderId is sourced from list_orders or the original send, and confirm is tied to human agreement and non-restorability. That goes modestly beyond the schema wording rather than merely restating it.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Cancel a letter or postcard') plus the exact scope ('sent with an arrival date and is waiting for its mail date'), and explicitly excludes Pay & Send orders and mail without an arrival date. An agent can distinguish this from siblings like request_send or send_letter without opening any schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit when-to-use conditions (arrival date set, mail waiting for its mail date), when-not conditions (Pay & Send orders, no arrival date), and the prerequisite flow (get orderId from list_orders or the send, then confirm: true only after the person agrees). Nothing about routing or preconditions is left to inference.

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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