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

Annotations already mark destructiveHint=true, but the description adds real-world consequence: 'this creates a real external send.' It also instructs the agent to inspect recipients/content before sending, reinforcing that this action is irreversible and has external impact. This goes beyond the bare annotation and provides valuable behavioral context.

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, no wasted words. The core action is front-loaded ('Send one exact existing draft'), followed immediately by the critical safety instruction. Every sentence earns its place.

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 two-parameter destructive action with no output schema, the description covers the essential pre-send verification step and discloses the external-send consequence. It doesn't describe return values, but that is less critical for a send action. Overall, the agent has everything needed to invoke the tool safely and correctly.

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 parameters are already well-documented in the input schema. The tool description itself adds little about parameter semantics; it references draft_id but not account_id. Per the rubric, with high schema coverage the baseline of 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?

The description states a precise verb and resource: 'Send one exact existing draft.' It clearly differentiates from sibling tools like email_create_draft, email_update_draft, and email_send by emphasizing it sends an already-created, exact draft rather than composing or modifying. No ambiguity remains about the tool's function.

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 provides a crucial operational condition: 'Resolve draft_id and inspect final recipients/content first when not already explicitly approved.' This tells the agent when it is appropriate to execute the send and what preconditions must be met. It does not explicitly name alternative tools or give a contrast to email_send, but the context and phrasing make the intended use clear.

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