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

The annotations only supply destructiveHint=true; the description adds the substantive behavioral facts an agent actually needs: the result is a draft rather than a send, sending is intentionally out of band, sender/reply-to addresses must already exist in the account, and the call returns the new campaign ID along with the underlying Moosend endpoint. This is material context beyond the annotation.

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?

Four compact sentences with zero filler: write mode and scope first, the not-sent guarantee second, content and sender requirements third, return value last. Each sentence carries distinct information and the most decision-relevant facts are front-loaded.

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 9-parameter write tool with no output schema, the description covers the write semantics, the human-gated send step, content sourcing, sender prerequisites, and the return value (the new ID). Nothing an agent needs in order to invoke this correctly is missing.

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 100%, so the schema already documents name, subject, sender_email, mailing_lists, and the rest. The description adds only two marginal clarifications — the html_content vs. web_location choice and the sender-account constraint (which the schema already states). Baseline 3 is correct here.

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 opens with a specific verb and resource ('WRITE: create a regular (non-A/B) DRAFT campaign') and narrows the scope in ways that matter: non-A/B, draft-only, and the fact that no email is dispatched. An agent can distinguish this from list_campaigns or get_campaign without opening any 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?

It states the operational boundary clearly ('It is NOT sent — sending stays a human action in Moosend'), tells the agent the two ways content can be supplied, and routes sender validation to the moosend_list_senders sibling. It stops short of spelling out full preconditions (e.g., what to do after creation), but the context for when to call it is explicit.

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