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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered. The description's real addition is the 'settings as configured' framing, which tells the agent the values are a configuration snapshot rather than live metrics. It says nothing about behavior when the id is unknown or whether the record is scoped to the caller's subaccount.

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 tight sentences: content first, then routing to the two siblings. No filler, and the most important disambiguation is front-loaded with the field list.

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 full annotations and no output schema, the description should convey return content, and it does name the primary sections. It stops short of an exhaustive field list or an error case, which is minor for a simple read-by-id tool.

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?

Single parameter with 100% schema description coverage that already explains the id comes from email_account_list. The description adds no syntax, format or lookup guidance beyond the schema, so the high-coverage baseline of 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?

Names the resource precisely ('one mailbox') and enumerates the returned surface: sending limits, warm-up state, signature, IMAP/SMTP settings. The final clauses explicitly separate it from email_account_stats (actual sending) and email_account_update (mutation), so an agent can route without opening a schema.

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 both when-to-use and when-not-to-use with named alternatives: use email_account_stats for what the mailbox actually sent, and email_account_update to change anything. The configuration-vs-performance distinction is the exact decision an agent needs to make here.

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