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

Annotations already cover readOnly and closed-world safety, so the bar is lower. The description adds genuinely new behavioral context: search spans subjects AND bodies, is limited to a single folder, and inherits list_emails' field order and paging semantics, which tells the agent the output shape without opening the schema.

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?

Three short sentences, front-loaded with the core action and scope, then the output-shape note, then the sibling pointer. 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?

An output schema exists, so return values needn't be explained, and the pointer to list_emails for field/order/paging semantics is a helpful shortcut. The only missing piece is explicit guidance on when to prefer this over list_emails.

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%, with descriptions for all six parameters including the limit cap and order enum, so the schema does the heavy lifting. The description only restates that query matches subject and body and that mailbox is a single folder, adding little beyond the schema.

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?

States a specific verb (search), resource (emails) and scope (one folder, subject and body text). It distinguishes itself from list_emails by noting results share fields/order/paging, but never states the substantive difference in selection (text match vs enumeration).

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 single-folder constraint is stated and list_mailbox_folders is named as the way to find other folders, which is useful context. However, there is no explicit 'use search_emails when you need to find messages matching text, use list_emails when you want to enumerate' guidance, so the choice against the closest sibling is left implied.

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