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

Annotations mark this as destructive and read-write, and the description adds deeper behavioral detail: irreversibility, recipient-list locking, inability to recall sent emails, refusal of empty `to` lists, and the promise that unsubscribed or suppressed addresses are never targeted. This goes well beyond the annotations and is consistent with them.

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?

Three focused sentences, front-loaded with an irreversibility warning, then scope, safety constraints, required confirmation workflow, and progress tracking. Every sentence earns its place and there is minimal redundancy.

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 destructive two-parameter send tool with full schema coverage and no output schema, the description covers invocation scope, edge cases, prerequisites, confirmation requirements, and monitoring. Nothing essential is missing for an agent to use it safely and correctly.

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%, giving a baseline of 3. The description adds meaningful parameter semantics: `to` restricts sending to active subscribers only, an empty list sends to nobody, omitting `to` sends to all active subscribers, and suppressed/unsubscribed addresses are excluded. This is valuable context beyond the schema, though `id` receives no extra explanation.

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 states a specific action: send a campaign, with explicit scope (all active subscribers in the workspace or restricted via `to`) and the locking of the recipient list. It is immediately distinguishable from siblings like preview_campaign_send, which only previews, and get_campaign_stats, which tracks progress.

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?

Provides a clear workflow: call preview_campaign_send first with the same parameters, then get explicit user confirmation and tell them the recipient count. It also points to get_campaign_stats for progress. It does not explicitly contrast with send_email or list when-not-to-use cases, but the sequencing guidance is strong.

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