gmail_send_email

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

Annotations mark this as non-read-only and open-world, but destructiveHint=false could mislead an agent into assuming reversibility — the description corrects this by stating 'It cannot be unsent'. That is the single most important behavioral fact for a send tool. It does not, however, address failure modes or whether a failed send is retried, so it stops short of a 5.

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, zero filler. The action and its irreversibility come first, with the alternative routed second — correct front-loading for a destructive-ish operation.

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 7-parameter, no-output-schema tool, the description covers the essentials: what it does, that it is irreversible, and where to go instead. It omits sibling alternatives like gmail_reply/gmail_forward, which matters for threading, but the core decision path is complete.

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 86%, so the schema already documents cc/bcc/html/attachments and their constraints (base64, ~4 MB cap). The description adds no parameter-level meaning beyond that, so the 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 an email') plus the operative modifier 'immediately from the connected account', which is exactly what distinguishes it from draft-creating siblings. An agent can place it precisely in the gmail_* family without opening a 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?

Explicitly names the safer alternative (gmail_create_draft) and the condition that selects it ('to let the user review first'). The irreversibility warning functions as a when-not-to-use rule; nothing is left to inference for the primary routing decision.

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