Send an email

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

Annotations already provide readOnlyHint=false, idempotentHint=false, and openWorldHint=true, but the description adds little behavioral context. It does not mention that sending is an external, irreversible side effect, nor does it disclose delivery-failure behavior, rate limits, or identity/authentication requirements. 'Standards-correct MIME' is a formatting detail rather than a behavioral disclosure.

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 one short sentence with the core action front-loaded: 'Compose standards-correct MIME and send it...' It is concise and easy to parse, though the phrase 'standards-correct MIME' contributes limited practical value for an agent selecting the tool.

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?

The schema covers all parameters and an output schema exists, so most invocation details are present. However, the description does not orient the agent within the large sibling set: it does not explicitly distinguish immediate sending from creating a draft or scheduling an email, and it omits caveats about the irreversible external effect of sending.

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 the baseline is 3. The description's 'selected identity' phrase loosely maps to the from_identity parameter but adds no new meaning beyond the schema, which already documents all seven parameters thoroughly.

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 uses the specific verb 'send' and clearly refers to composing and delivering an email, with the added context of using a selected identity. This distinguishes it from siblings like create_draft and schedule_email, which do not immediately 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?

The description implies the usage case: compose and send an email now through an identity. However, it gives no explicit when-to-use or when-not-to-use guidance, and it does not name alternatives such as create_draft, schedule_email, or reply_email.

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