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

Discloses behavior that annotations cannot convey: external reach (openWorldHint restated with meaning), a multi-minute hold before delivery, and cancellability from Relaticle notifications or Outbox, which softens the destructiveHint=true. It omits the 20-recipient cap and signature default, though both are in the schema. Strong added context, short of exhaustive.

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?

Five short sentences, front-loaded with the action and the consent gate before mechanics and alternatives; nothing is buried. Slight redundancy where the body-format sentence repeats the schema description exactly.

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 high-blast-radius send tool with annotations and an output schema already present, the description supplies the missing decision-relevant context: consent requirement, delay window, cancellation path, and sibling routing. Only the recipient limit and signature behavior go unmentioned, and those live in the schema.

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 all nine parameters are already documented; the description mostly restates them ('body as plain text or markdown' duplicates the schema). 'Pass scheduled_for to send later' adds a use case rather than new syntax, so the marginal value is modest. Baseline 3 is appropriate.

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 and resource ('Send an email as the current user from one of their mailboxes') plus the scope of the send (reaches people outside the workspace). It is clearly distinguishable from create-email-draft-tool and send-email-draft-tool, which it names directly.

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 an explicit gating condition ('call this only when the user asked for it') and names the alternative with the selecting condition ('Prefer the create email draft tool when the user wants to review before sending, then send that draft with the send email draft tool'). When-to-use and when-to-use-something-else are both stated.

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