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

Annotations already indicate this is a write operation (readOnlyHint=false), non-destructive, and idempotent. The description adds the user-approval constraint but does not disclose further behavioral traits like rate limits, delivery confirmation, or error handling. No contradiction with annotations.

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 concise: two sentences, no redundancy. First sentence states purpose, second gives usage guideline. Every word is useful.

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 complex tool with 13 parameters and low schema coverage, the description is minimal. It covers the core action and approval context but lacks guidance on parameter choices (e.g., when to use html vs text, how attachments work). The presence of an output schema offsets the lack of return-value description.

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?

With only 15% schema description coverage, the description should compensate but fails to explain any parameters. It provides no guidance on required fields (mailbox_id, to, subject) or optional ones (html, text, attachments). The schema has some descriptions but the tool description adds none.

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 clearly states the tool sends an email from a mailbox ID. It uses a specific verb ('send') and resource ('email'), and distinguishes from sibling reply tools by focusing on composing new messages rather than replying to existing threads.

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 explicitly advises using the tool only after user confirmation: 'Use only after the user has explicitly asked to send or approved the exact recipients and content.' This provides clear context, though it does not explicitly name alternatives like reply tools.

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