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

Annotations already flag the operation as destructive and non-read-only. The description adds useful behavioral context beyond the annotation: it replaces at the current version, every edit requires user review, and the operation never sends the draft. This gives an agent useful expectations about workflow consequences, though it does not detail irreversibility or conflict handling.

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?

The description is two short sentences with no filler. The primary action 'Replace a pending draft at its current version' is front-loaded, and the second sentence efficiently communicates the key behavioral constraints (user review required and no sending).

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 six-parameter destructive tool with no output schema and no parameter descriptions, the description is thin. It conveys the core workflow and safety caveat, but it does not explain how to obtain the current version, what happens after a successful revision, or whether the draft remains pending. These gaps could lead to an agent guessing about prerequisites or return behavior.

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 0%, so the description must compensate by explaining what parameters mean spans. It does not explain draftId, version, to, subject, text, or cc; only the phrase 'at its current version' hints at the version parameter. The schema provides types and constraints but no semantic meaning, leaving the agent to infer the fields from their names.

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 clearly states the specific verb 'Replace' with the resource 'pending draft' and adds a distinguishing qualifier 'at its current version.' It separates this tool from read-only siblings like get_draft and creation/forwarding tools like prepare_draft and prepare_forward, so an agent can identify what it does without inspecting other tools.

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 implies when to use the tool: any time a pending draft must be revised. 'This never sends' rules out using it as a sending operation stanchion, which is helpful. However, it does not explicitly name alternatives such as prepare_draft for initial drafts or get_draft for retrieving the current version, and it provides no when-not-to-use guidance.

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