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

With no annotations, the description carries the full burden and does well: it discloses latency ('can take minutes'), cost ('No credits'), and absence of side effects ('Nothing is sent'). It stops short of stating prerequisites (e.g. campaign must be in draft/prepared state), whether the call is idempotent, or what to do on failure — gaps for a long-running preparation job.

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 sentence plus two short fragments; the scope constraint is front-loaded and every clause adds a distinct fact (scope, latency, no send, no cost). 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?

Covers applicability, latency, cost, and side effects, and the input schema is fully documented. It leaves out what the tool returns/produces and the failure/retry path, but with a single param and no output schema the definition is nearly complete for correct invocation.

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?

Single parameter with 100% schema coverage and a schema description that points to list_campaigns, so the baseline is 3. The description adds no additional meaning about the id (e.g. that it must be a legacy company-based campaign for the call to succeed).

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+resource (generate emails for every contact) plus timing (ahead of sending), which cleanly separates it from send_campaign_emails_now, preview_campaign_email, and retry_campaign_email_preparation. The 'legacy' scope further narrows it.

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 names when to use it (legacy company-based audiences) and when not to (people/custom-audience campaigns prepare automatically after launch, so no call is needed). That is a clear condition plus exclusion, which is exactly what an agent needs to route correctly.

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