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

Annotations already flag destructiveHint=true and idempotentHint=true, but the description adds genuinely new context: the action is irreversible through the API and the contact can only return via a sign-up form. That is precisely the consequence an agent needs before calling a destructive tool.

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 tight sentences: mutation type and effect first, irreversibility second, use case third. No redundant restatement of the title, and the endpoint is appended where it aids verification.

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 the essentials for a destructive, idempotent 2-param write tool with no output schema: what it does, that it cannot be undone, and when to use it. Minor gap is what happens on an already-unsubscribed or nonexistent contact, though idempotentHint partially signals this.

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%, with the email/member_id XOR rule already documented per-parameter. The description adds no additional semantics (no format, precedence, or behavior when a contact is unknown), so the baseline 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?

States a specific verb and resource ('unsubscribe a contact so Robly stops emailing it') plus the underlying endpoint POST /api/v1/contacts/unsubscribe. The 'WRITE:' prefix and the unsubscribe action cleanly separate it from siblings like robly_subscribe_contact and robly_remove_contact_from_list.

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?

"Use it for a contact that asked to stop" gives a clear triggering condition for when to invoke this over alternatives. It does not explicitly name the sibling tools (e.g. robly_subscribe_contact) it is contrasted with, so it stops short of full when/when-not routing.

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