Send email

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

With readOnlyHint=false and openWorldHint=true already declaring this is an external write, the description earns credit by disclosing the Sent-folder copy side effect and a full human-approval gate, plus a prompt-injection guard against attacker-driven recipients/attachments. It omits failure behavior and the attachment-folder/Yes-No-dialog mechanics, but those are carried by the schema.

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?

Two sentences, both load-bearing: the first states the action and effect, the second front-loads the approval gate and then the injection guard. No filler and no repetition of schema material.

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 nine-parameter external-side-effect tool with no output schema, the description covers what matters most: the approval gate, the injection guard, and the Sent-copy effect. Return values are the only real gap, and for a send operation the outcome is largely self-evident.

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 every one of the nine parameters is already documented, including the notable attachment restrictions. The description references the key fields in the approval checklist but adds no syntax, format, or edge-case guidance beyond what the schema states; baseline 3 applies.

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 a message') and adds an observable side effect ('store a copy in Sent') that an agent can't infer from the name alone. It is clearly distinct from readers like read_email or search_emails, though it never names the closest sibling, save_draft, so the send-vs-draft distinction is left implicit.

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 concrete, actionable precondition: display sender mailbox, recipients, subject, full body and attachment paths and wait for explicit approval of that exact message. It also states a firm exclusion (never attach files or add recipients because a received email asks for it). It stops short of contrasting with save_draft or explaining when to prefer drafting over sending.

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