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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the description's key contribution is the irreversible consequence: rules 'cannot be removed afterwards by any tool.' That is exactly the kind of context annotations cannot convey. It does not address idempotency (annotations say not idempotent), so whether duplicate keywords are silently doubled is left unclear.

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?

Two tight sentences: the bulk-vs-single relationship and the irreversible warning are both front-loaded, and there is no filler or redundancy with the schema.

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 an irreversible bulk mutation with no output schema, the description supplies the one piece an agent most needs — that the effect cannot be undone. It leaves open what happens to a 5,000-entry payload that partially fails and what the response reports, which is a real gap for a bulk operation but a minor one given full schema coverage.

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% and both parameters are documented inline, including the type enum and keyword matching semantics, so the schema does the heavy lifting. The description's examples ('competitor domain list, or an opt-out export') loosely illustrate what entries look like but add no format or constraint detail beyond the schema (e.g. the 5,000 cap comes from the schema).

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 verb and resource ('add many exclusion rules at once') and explicitly relates it to the sibling `blacklist_add` ('same effect as `blacklist_add`, one call'), so an agent can distinguish bulk from single-add without opening either schema.

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?

It gives clear usage context (a competitor domain list, an opt-out export) and implicitly routes single additions to `blacklist_add`, plus a procedural prerequisite to review the list with the user. It stops short of explicit when-not conditions, such as what to do on partial failure or whether to prefer `lead_blacklist` for individual leads.

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