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

Annotations already declare destructiveHint=true and idempotentHint=false, so the safety profile is covered. The description adds genuinely useful non-annotation behavior: on IMAP the ID encodes folder + UID and changes when the message moves, so the id from the last operation must be reused. That volatility caveat is real behavioral context beyond the structured fields.

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 lead sentence is well front-loaded, but the description then duplicates the long ID-resolution paragraph that already appears in the schema, so several sentences do not earn their place by adding new information. Net effect is redundancy rather than sharp concision.

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?

With 100% schema coverage, destructive annotations, and no output schema required, the definition supplies everything needed to invoke correctly: the target ID source, the required resolve-first step, and the ID-stability caveat. Only the trash-vs-permanent-delete distinction is left unstated.

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 description coverage is 100%, and the email_id guidance in the description is essentially a verbatim repeat of the schema text, adding no new meaning. The account_id semantics (multi-account disambiguation) are likewise already fully documented in the schema, so the baseline 3 applies.

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 and resource ("Trash one exact email") with clear single-message scope, which separates it from bulk or move/label operations like email_move_or_label. It does not explicitly name the sibling it differs from, and leaves some ambiguity about whether "trash" means move-to-trash-folder (recoverable) versus permanent removal, so it stops short of a 5.

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?

Gives one prerequisite ("Resolve email_id first") and flags the destructive nature, which implies when to use it. However, it never names an alternative (e.g., email_move_or_label to relocate instead of trash) or states when-not-to-use, so usage is only implied rather than spelled out.

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