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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false), so the bar is lower, and the description adds real value beyond them: it discloses that removals come with reasons and that the clean CSV is only returned when it is 500 rows or fewer. That output-size threshold is exactly the kind of behavioral constraint annotations cannot express. It stops short of describing the failure case when the list exceeds 500 rows or what the 'why' values look like.

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?

A single dense sentence that front-loads the action, then the mechanism, then the return behavior. No filler and nothing implied by the schema is restated.

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?

With annotations covering safety and no output schema, the description adequately explains what is returned and the 500-row guardrail. Two gaps remain for a 5: how the two suppression input parameters interact, and what happens when the output exceeds the row limit.

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 all five parameters are already documented, and this is the baseline case. The description reinforces the semantics of matchDomains and maxPerCompany ('whole suppressed domains', 'per-company cap') but adds no syntax or format detail beyond the schema, and it does not clarify the mutual exclusivity of the suppression vs suppressionCsv input paths.

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 (check a campaign list against a do-not-contact list) plus the matching mechanics (exact email matches, optional domain matching, per-company cap). An agent can tell this is a filtering/screening operation rather than a mutation. It does not explicitly differentiate from the adjacent clean_csv or verify_email siblings, which keeps it from a 5.

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?

The phrase 'before sending' gives a clear temporal/process context for when to invoke the tool, which is actionable. However, it never names alternatives or exclusions (e.g., when to use clean_csv or verify_email instead, or whether this replaces or complements them).

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