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

Annotations already declare destructiveHint=true and openWorldHint=true, so the irreversibility warning is partly redundant. The description nonetheless adds genuinely new behavioral context: the account-bound computer:write OAuth requirement, that a prompted local owner approval may gate execution, and that the recipient must be external. It says nothing about failure behavior 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?

Three tight sentences with the irreversible-send constraint and approval gate front-loaded, followed by verification and the alternative. Every sentence carries distinct information with no padding.

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-parameter, no-output-schema mutation tool, the description covers the safety profile, auth prerequisites, pre-send checks, and the sibling fallback. Minor gaps remain around the meaning of 'to' and what a failed send returns.

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 coverage is 100%, so the baseline is 3. The description only loosely gestures at the parameters ('check recipients, subject and content') and does not resolve the confusing schema text for 'to', which reads like a file-path destination, nor does it say whether multiple recipients are accepted. It adds little beyond the schema.

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+resource (send email message) and adds scope (external recipient, irreversible) that narrows it well below the generic name. It explicitly distinguishes itself from exza_create_email_draft, so an agent can route between the two without opening either 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 a clear when-to-use rule: send directly when approval has been obtained, otherwise fall back to exza_create_email_draft for human review. It also instructs the agent to verify recipients, subject and content first. It misses the other obvious alternative, exza_preview_email_message, which an agent might want for verification.

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