send_email

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

Annotations already flag destructiveHint=true and readOnlyHint=false; the description does not contradict these. It adds genuine behavioral context beyond annotations by disclosing the hosted-auth-link failure mode and the retry/account-setup follow-up, which an agent needs to handle the no-mailbox case gracefully.

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 description is front-loaded with the core purpose, followed by hard usage constraints, the auth-failure flow, and a compact Args block. Every sentence earns its place—there is no filler or re-statement of the schema titles.

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 4-parameter mutation tool with an output schema and full annotations, the description is nearly complete: it covers purpose, exclusions, auth failure, and parameters. Minor omissions are details like success-path behavior and rate limits, but the output schema already carries return-value documentation, so nothing critical is missing.

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's Args block carries the full parameter-documentation burden. It explains all four parameters and adds meaningful notes beyond the bare titles: 'HTML is fine' for body and 'Optional' for to_name. Coverage is complete, though the individual descriptions are terse.

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: 'Send an email through the connected Unipile mailbox (Gmail/Outlook).' It also distinguishes itself from siblings by declaring 'This is the only supported way to send email,' separating it from tools like send_message and generate_and_send.

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?

Explicit when-not guidance is present: 'Never use Mail.app, osascript, mailto: handlers, or a local SMTP client.' It also provides a concrete alternative path for the unauthenticated case ('call account(action="connect_email") first') and instructs the agent to have the user open the hosted-auth link and retry.

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