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

Annotations declare a non-read-only, non-destructive write; the description adds the key behavioral fact that nothing is sent, plus the return value (draft uid). It does not cover auth/permission needs or overwrite semantics, but for a create operation with annotation coverage this is a solid addition beyond structured fields.

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 tight sentences: purpose first, then usage guidance with the alternative, then the return value. Every sentence carries distinct, non-redundant 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?

With no output schema, the description usefully discloses the return value (uid) and covers purpose and usage for a 10-parameter tool. It is nearly complete; only prerequisites such as mailbox existence or draft-folder behavior are unaddressed.

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 90%, so the schema already explains every parameter including the 'may be left out and filled in later' note on 'to'. The description adds no parameter syntax or constraints of its own, so the 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 (save a message in the Drafts folder) with the critical qualifier 'WITHOUT sending it'. This immediately separates it from send_message and send_draft, so an agent can route correctly without opening a schema.

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?

Explicitly gives the when-to-use condition ('when a person should review a message before it goes out') and names the follow-up alternative (send_draft later, or the user sends from their mail app). Nothing about selection is left to inference.

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