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

Goes beyond the annotation by clarifying that this write does not trigger a send, that content may come from HTML or a fetched URL (with CSS inlining), that sender addresses must pre-exist in the account, and that the new campaign ID is returned. The 'WRITE:' framing is consistent with destructiveHint=true, so there is no contradiction.

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 tight sentences: the write/draft/no-send semantics come first, then content sourcing, then prerequisites, then the return value and endpoint. No filler.

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 supplies the essential return info (the new campaign ID) and covers the two non-obvious constraints (content source, sender validation). Remaining gaps are minor, e.g. whether mailing_lists targets are validated against existing lists.

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 100%, so the baseline is 3, but the description adds real meaning: html_content and web_location are alternative content sources rather than complementary, and sender_email/reply_to_email must resolve to account senders (a validation constraint not stated in the schema).

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 (create), the resource (draft campaign), and an important scope qualifier: regular, non-A/B. This lets an agent separate it from any A/B-test creation or sending path without opening the 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?

Explains the key usage context — the result is a draft and is never sent, sending remains a human action — and gives prerequisites for sender_email/reply_to_email with a pointer to moosend_list_senders. It does not name a sibling for reading/updating the campaign afterward, so it falls just short of explicit alternatives.

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