Set Mailbox Rules

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

Annotations already mark it as destructive and not read-only; the description adds behavioural context by stating 'replace every' and 'preserve any rules that should remain', which clarifies the full replacement nature. No contradiction with annotations.

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?

Two sentences with no superfluous text. The first sentence states the action, the second provides critical operational guidance. Every word earns its place.

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 tool with a complex nested input schema, the description provides essential operational context (fetch-first, replace-all) that compensates for the schema's detail. The presence of an output schema further reduces the need to describe return values.

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?

The schema covers 67% of parameters with descriptions, but the description adds semantic guidance by explaining that the 'rules' parameter should contain the final set of rules and that existing rules should be fetched and preserved. This adds meaning beyond the schema itself.

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 verb 'Replace' and the resource 'every deterministic server-side inbox rule for a mailbox'. It distinguishes itself from sibling tools like 'shipmail_get_mailbox_rules' by indicating a write operation and providing a prerequisite step.

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?

Explicitly instructs the agent to call shipmail_get_mailbox_rules first and preserve any rules that should remain, which serves as a clear when-to-use and how-to-use guide. However, it does not explicitly state alternatives or when not to use it.

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