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

With no annotations supplied, the description carries the full burden, and it does disclose the single most important behavioral trait: the draft is not sent without explicit user confirmation. It omits other relevant behavior such as where the draft is stored, whether it requires an authenticated Gmail scope, and what the call returns (e.g., a draft ID), leaving meaningful gaps for a mutation tool.

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 short sentences with zero filler, and the core purpose is front-loaded before the safety caveat. Nothing could be removed without losing information.

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 four-parameter mutation tool with no annotations and no output schema, the definition covers purpose and the send-safety constraint but leaves the agent without knowledge of return values, draft destination, or authentication requirements. It is adequate to invoke the tool correctly but not 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 100%, so all four fields (to, cc, subject, body) are already documented in the schema, including that body accepts plain text or markdown. The description adds no parameter-level meaning beyond that, so the baseline of 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?

The description states a specific verb and resource ('Create an email draft in Gmail'), which is unambiguous and clearly distinct from read-oriented siblings like gmail_search_messages. It stops short of naming a sibling alternative, but the resource boundary is clear enough for selection.

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?

Usage is only implied by the verb 'draft' – the agent can infer this is the non-sending path, but the description never says when to prefer it over, for example, slack_post_message_draft or a direct send flow. There are no explicit exclusions or prerequisites, so the agent must infer the routing.

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