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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds the useful fact that this is a pure MJML-to-HTML transform, which is consistent with idempotency, but says nothing about whether the referenced campaign must exist, whether anything is stored, or how large MJML is handled.

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?

A single front-loaded sentence with no filler; the verb and output are stated first. It could have used the remaining space for the parameter or usage detail it lacks, but there is no wasted wording.

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 two-parameter, no-output-schema transform tool this is minimally adequate: the operation and its product are named. It falls short on what 'id' identifies and on whether an invalid id or malformed MJML produces an error versus partial HTML, which an agent needs before calling.

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% for both required parameters, so the description must compensate. It clarifies that 'mjml' is MJML source belonging to a drag-and-drop campaign, but leaves 'id' completely unexplained — campaign id, template id, or draft id is ambiguous, which matters for a call that will fail or render the wrong content if wrong.

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 transformation: renders a campaign's MJML into preview HTML. An agent can tell it produces preview markup rather than fetching or sending email, but the description never names a sibling (e.g., get_email_format or send_test_email) to sharpen the boundary.

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?

No when-to-use or when-not-to-use guidance is given, and no alternative is mentioned. The only hint is the phrase 'for the email preview view', which implies a UI-rendering context but leaves the agent to infer that this is not for sending or persisting anything.

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