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

Annotations cover safety (non-destructive, idempotent), and the description adds substantial context beyond them: auth requirement, unscoped-key/owner_manage scoping, the 409 owner_style_locked failure mode, and the guarantee that the note is never surfaced in emails. This is exactly the extra behavioral detail the dimension rewards.

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 the usage trigger and scoping decision, then error and behavior notes; every sentence carries information. It is dense and long, but there is little wasted wording beyond minor repetition of the null semantics.

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 covers the return contract by noting it mirrors cooper_get_owner_preferences, and it supplies auth, scoping, error, and downstream-effect details. An agent has everything needed to call it 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 coverage is already 100%, so the baseline is 3, but the description adds the pairing rule that inbox_id and owner_id must be supplied together to target one owner and that omitting owner_id sets the account default. Style null-inherits and note null-clears mostly restate the schema, so this is above baseline but not fully additive.

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 ('Sets the account default... or one owner's style') and cleanly separates the two scopes an agent must choose between. It also positions itself as the setter counterpart to cooper_get_owner_preferences, which is the obvious sibling.

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 names the trigger ('when the human asks for shorter, longer, or friendlier email'), the two operating modes with the exact parameters that select them, and an explicit exclusion ('A style the owner chose from the Change email style link... cannot be changed here: 409'). No inference is required.

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