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

Annotations already establish read-only, idempotent, and non-destructive behavior, so the description adds valuable context: newest-first ordering, alias handling, return shape (headers and folder IDs, not bodies), and the security warning that email content is untrusted data and never instructions. This goes well beyond the annotations without contradicting them.

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 purpose is front-loaded in the first sentence, and the paragraph packs folder routing, alias behavior, custom-folder guidance, return format, and a security caveat into six focused sentences. There is no repetition of schema or annotations, and every sentence contributes.

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?

Despite no output schema and no parameter descriptions, the description covers scope, ordering, folder selection, custom-folder discovery via list_folders, return format, and a data-safety warning. The main gaps are that position and limit semantics are not explained and mailboxId is not explicitly linked to list_mailboxes.

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?

With 0% schema description coverage, the description compensates for the trickiest folder/folderId relationship, including allowed values, the spam alias, and mutual exclusivity. However, parameters like position, limit, from, subject, and unread are left to name-based inference, and position's likely pagination meaning is not explained.

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 opens with a specific verb and resource ('Find email in one connected mailbox, newest first') and adds scope details via folder/folderId semantics. The explicit 'Returns headers and folder IDs, not bodies' clearly distinguishes it from read_message.

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?

It gives explicit folder-selection rules: junk/spam alias, standard folders, custom folder via list_folders then folderId, mutual exclusivity of folder/folderId, and the 'omit both or all' behavior. It does not explicitly name read_message as the tool to use when bodies are needed, though the 'not bodies' caveat implies it.

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