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

Annotations already declare readOnlyHint=false, openWorldHint=true, and destructiveHint=true, so the agent knows this is an outward-facing write. The description adds the useful constraint that only plain-text is supported and that mail comes from the connected account, but says nothing about irreversibility, delivery confirmation, or rate limits.

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?

One short sentence, front-loaded with the verb and resource and free of filler. It is efficient, though its brevity leaves no room for the usage context a mutation tool would benefit from.

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?

A 3-param write tool with rich annotations and full schema coverage, so the safety and input story is largely covered. However, no output schema exists and the description says nothing about what happens after the send or how failures are surfaced, leaving it merely adequate.

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%, so to/subject/body are already documented in the schema. The description's 'plain-text' note loosely reinforces the body constraint but adds no syntax, format, or multi-recipient detail beyond what the schema provides.

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 (send) and resource (email) with a scope qualifier (plain-text, from your connected account). The action verb clearly separates it from sibling email tools like email_list_recent, email_read, and email_search, but it never names those siblings explicitly.

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 description offers no when-to-use guidance, no prerequisites, and no alternatives. It does not say when to prefer this over beeper_send_message or telegram_send_message, nor mention any constraint such as needing a connected account before calling.

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