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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is partly covered. The description adds genuinely new behavioral context beyond them: list memberships are preserved rather than deleted, delivery stops everywhere, and the only reversal path is re-signup with email confirmation. It does not discuss permissions or response behavior, which keeps it short of a 5.

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 short sentences, front-loaded with the effect, then the input convention, then reversibility, then what persists. Each sentence carries distinct information and none repeats structured fields verbatim.

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 two-parameter tool with no output schema and full annotation coverage, the description covers effect, inputs, reversibility, and data retention — enough to call it correctly. It leaves open what happens if the id is unknown or whether a non-contact email creates a record, which keeps it from a perfect score.

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 description coverage is 100%, so both parameters are already documented, and neither is required. The description merely restates the either/or choice ('id or the email address') without adding format, precedence, or error behavior when neither is supplied, so the baseline of 3 applies.

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 opens with a specific verb and effect: 'Records that someone has opted out, so no list or campaign emails them.' This is more precise than the title 'Unsubscribe contact' and makes the outcome (suppression across lists and campaigns) unambiguous, so an agent can distinguish it from contact-mutation siblings like update_contact or tag_contact.

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?

Usage is implied by the purpose (call it when someone opts out), and the sentence 'Give the contact's id or the email address' tells the agent which imperative to satisfy. However, no explicit when-not guidance or alternative tool is named, so the routing logic is left to inference.

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