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

Annotations already declare destructiveHint=true, idempotentHint=false and openWorldHint=true, and the description goes meaningfully beyond them: pre-save validation, sanitization without a browser, 400 VALIDATION_ERROR surfacing, per-side 2 MB cap, the confirmation gate, and the note that writes are never retried automatically. The notable gap is PATCH merge semantics — it never says whether omitted fields are left untouched, which matters most for a partial-update tool.

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 first two sentences are pure waste, and the validation/canvas rules are dumped as one long run-on block. The substantive content is dense and front-loaded well enough, but the duplicated HTML constraints and the redundant opening cost it structure points.

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 destructive, nested-body update tool with no output schema, the HTML authoring constraints, size limits, error behavior and approval requirement are all covered in useful detail. What is missing is the core update contract: which body fields are optional, whether the operation merges or replaces, and what a successful response contains.

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 33%; the id and confirmed parameters are already documented in the schema, and the html_front/html_back field descriptions repeat the body text almost verbatim, so the description adds little there. It does clarify the publish interaction by noting that publishing revalidates both draft sides, but name, theme and layout remain unexplained in both schema and description.

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 opening two sentences ('Update design. Update a design.') merely restate the name and title, which is near-tautological. The rest of the text reveals that the tool updates a mail design's HTML sides and can publish the draft, but it never enumerates the other mutable fields (name, theme, layout) or distinguishes itself from siblings like dealmachine_post_mail_designs or dealmachine_patch_mail_campaigns_id.

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?

There is real conditional guidance about publishing ('Publishing... requires complete front and back HTML') and a hard prerequisite ('Requires user approval and confirmed=true'), which is more than implied usage. However, there is no statement of when to choose this over the create endpoint or the get endpoint, and no exclusion or typical workflow context.

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