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

Annotations already declare idempotentHint=true, destructiveHint=false and readOnlyHint=false, but the description adds real context beyond them: nothing is sent, the human still presses Send, discarding is a throwing-away action, and idempotency_key must be reused across retries. What remains undisclosed is whether discarding is reversible and what the response returns, which keeps it from 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?

Three dense sentences, each front-loaded with the highest-value information: what it does first, then the no-send safety fact, then id and retry mechanics. No filler or restatement of the tool name.

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 mutation tool with no output schema, the description covers the essential contract: scope, mutation safety, id provenance, and idempotency. It falls short only on the semantics of isReady, whyNote, and the 'active' status value, which an agent would have to guess.

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 only 14% (just idempotency_key), so the description does meaningful work by identifying editable fields, flagging subject as email-specific, and explaining status 'discarded' and the draft_id origin. However, the meaning of 'isReady' and 'whyNote' is never explained, and the 'active' enum value is left unaddressed, so several parameters remain semantically opaque.

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 names a specific verb and resource ('Edits a draft in a conversation's draft box') and enumerates the exact fields that can change: body, subject, whyNote, isReady, and status 'discarded'. It also implicitly separates itself from create_draft (source of draft_id) and send_email ('Nothing is sent'), so an agent can pick it out of a large sibling list.

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?

It gives clear usage context: use it to modify an existing draft, use status 'discarded' to throw the draft away, and get draft_id from create_draft or read. Retry behavior is spelled out ('Pass the same idempotency_key when retrying'). The only gap is the absence of an explicit 'use create_draft instead when starting a new draft' exclusion, though that is strongly implied.

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