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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds real context beyond that: the write-permission requirement and the fact that archiving is recoverable via unarchive, which explains why destructiveHint is false. It omits idempotency behavior (e.g., archiving an already-archived thread) and the effect scope on the whole thread.

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, no filler, with the operation list front-loaded and the permission/recoverability caveats following. Every clause 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 3-required-param mutation tool with no output schema, the description covers the action set, the permission requirement, and reversibility of archive. It lacks detail on what happens for already-archived/read threads and whether the change spans the entire thread, but the coverage is close to sufficient.

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 0%, so the description must carry parameter meaning. It does gloss the action values ('archive, undo archive, or set read state' mapping to archive/unarchive/read/unread), but gives no explanation of threadId or emailAccountId beyond their self-explanatory names. Partial compensation only.

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 names a specific resource (a thread in the selected mailbox) and enumerates the exact operations available: archive, unarchive, read, unread. This clearly separates it from siblings like read_mail/open_mail, since the verb is state mutation rather than retrieval. It stops short of explicitly naming which sibling to prefer, which holds it at a 4.

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 states a prerequisite ('Requires account write permission') and notes that archive can be reversed with unarchive, which implies when each action is appropriate. However, it never says when to use change_mail versus siblings like open_mail, read_thread, or search_inbox, so guidance is implied rather than explicit.

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