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

Annotations already declare destructiveHint=true and idempotentHint=true, but the description adds real behavioral context beyond them: the batch is all-or-nothing so one bad address rejects everything, the block is persistent for future sends, and user confirmation is expected before committing. That is exactly the extra layer annotations cannot express.

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?

Front-loaded with the core action and the most dangerous misconception (it will not stop Marketing Platform campaigns) before the scope taxonomy. It is dense and every sentence carries information, though the scope explanation partially repeats what the schema property descriptions already say.

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, open-world mutation with no output schema, the description covers effect, persistence, scope semantics, failure mode, and the safe preview-then-confirm protocol. An agent has everything needed to call it correctly and responsibly.

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 baseline is 3, and the description earns above that by explaining the failure semantics of the emails batch (all-or-nothing) and reinforcing the confirm/dry_run workflow rather than just restating the enum. The scope definitions largely duplicate the schema text, which caps it below 5.

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?

Specific verb+resource ('Add recipients to the API Platform suppression list') with the effect stated ('rejected on future API Platform sends'). It explicitly carves out what it does NOT do ('does NOT stop Marketing Platform campaigns') and names the sibling that handles that case (update_contact), so an agent can separate it from the many other add_* and contact tools.

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?

Gives explicit when-to-use (API Platform sends), when-not-to-use (Marketing Platform campaigns), and the alternative path (unsubscribe via update_contact or panel import). It also prescribes the operating procedure: preview with dry_run/omitted confirm, show the user, then confirm.

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