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

Annotations already declare a non-readonly, non-destructive, non-idempotent write; the description adds context annotations cannot carry: output is a DRAFT, nothing is sent, the failure mode for SENT campaigns, the returned id, and the underlying endpoint. This is exactly the value-add expected of a description on top of annotations.

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?

One dense sentence plus return-value and endpoint notes, front-loaded with the WRITE and DRAFT framing. Every clause carries information; nothing is 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?

For a single-parameter write tool with no output schema, the description covers action, result (new campaign id), safety (draft only), and the main error condition. Nothing an agent needs to call it 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?

With 100% schema coverage and a single required parameter, the schema already documents campaign_id ('The campaign to copy.') so the baseline is 3. The description earns an extra point by adding a validity constraint on that id — SENT campaigns will fail — which the schema does not express.

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 resource ('copy an existing campaign into a new DRAFT') and immediately disambiguates from sibling create_campaign and send_campaign by clarifying that nothing is sent. An agent can distinguish this from update_campaign or create_campaign 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?

Explicitly states the preclusion: a SENT campaign cannot be cloned (HTTP 500). That is real when-not-to-use guidance. It stops short of naming the alternative tool (e.g., create_campaign) for the blocked case, so it lands at 4 rather than 5.

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