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

Adds a great deal beyond the readOnly/idempotent annotations: required scopes ('read:email' plus 'manage:drafts'), the concurrency hazard that the user may edit or send with no notice, the specific 'already sent' response, the host's one-line summary instead of opening a second editor, and the untrusted_content flag. This is exactly the kind of context annotations cannot convey.

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?

Front-loaded with purpose and return values, then the cautions. It is dense and one sentence ('so this read is its current subject, recipients and sent state') is awkwardly worded, but nearly every sentence carries operational value.

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?

With an output schema and full annotations already present, the description still covers the gaps that matter: auth scopes, stale draft_id risk, send-race behavior, and untrusted content flagging. Nothing an agent needs to call it safely is missing.

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 coverage is 100% and the draft_id instability-on-save caveat is already in the schema, so the description adds little parameter-specific detail. Its note about the read reflecting 'current subject, recipients and sent state' is behavioral rather than a parameter clarification, so 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 ('Get the current text of one unsent draft') plus the fields returned, which separates it from draft_list (listing) and email_read (a received message). The concrete scenario ('before revising a draft the user edited in the draft editor card') makes the scope unmistakable.

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 clear trigger case (re-reading a draft after the user edited it) and implicitly excludes listing via the 'one draft' framing, but never explicitly names draft_list or email_read as the alternatives an agent should consider instead.

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