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

Annotations already mark this as destructive, but the description adds substantial operational context: the lead's sequence stops, they are excluded from every future campaign, the effect is account-wide and lasting, and no tool removes a blacklist entry. That is exactly the kind of irreversible behavior an agent needs to know before invoking.

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?

The description is front-loaded with the effect of the call, then the usage condition, then the durability warning, then the alternative. Every sentence contributes to safe tool selection and none is redundant.

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 one-parameter destructive mutation with no output schema, the description covers purpose, usage, irreversible behavior, and the safer alternative. An agent has everything needed to decide whether to call it and what consequences to expect.

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?

The schema has 100% description coverage for the single parameter and already states that `leadId` comes from `lead_list`. The description does not add parameter-specific semantics beyond that, so the baseline of 3 is appropriate.

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: adding a lead to the blacklist. It also specifies the account-wide, lasting scope and the immediate effect of stopping the lead's sequence, so the purpose is unambiguous.

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 identifies this as the right response to an opt-out request and gives a clear when-not/alternative: use `lead_update` with `isExcluded: true` to stop sending without permanent exclusion. It also adds a strong prerequisite: confirm the person and get an explicit yes before calling.

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