Update Scheduled Message

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

Annotations already provide `destructiveHint: true`, indicating state mutation. The description's 'Replace' aligns with this. However, it adds no new behavioral context beyond the annotations, such as effects on other operations or prerequisites.

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 description is a single sentence, concise and front-loaded with the verb 'Replace'. It efficiently conveys the core functionality, though it could be slightly more structured.

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?

Given the presence of an output schema, return values need not be explained. The description covers the main purpose but misses details like validation rules, idempotency handling, and error conditions, which would be helpful given the tool's complexity (12 parameters).

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 very low (17%), with only `id` and `idempotency_key` having descriptions. The tool description lists replaceable fields (recipients, content, etc.) but does not elaborate on formats, constraints, or semantics for the 12 parameters. The description does not compensate for the low schema coverage.

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 clearly states the action ('Replace') and the resource ('future scheduled message'), listing specific fields (recipients, content, staged attachments, delivery time). It distinguishes itself from siblings like `shipmail_get_scheduled_message`, `shipmail_list_scheduled_messages`, and `shipmail_cancel_scheduled_message` by being the update operation.

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 phrase 'before dispatch begins' implies the tool should be used on unsent messages, but it does not explicitly state when not to use it or mention alternatives (e.g., `cancel_scheduled_message`). The context is clear but lacks exclusionary guidance.

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