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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered structurally. The description adds real value by disclosing the downstream effect (future sends blocked), but says nothing about idempotent re-add behavior, whether existing contacts are affected, or error conditions. Adequate but not rich.

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 with the action front-loaded and the consequence second. No filler, no redundancy, and the important scoping fact (blocking future sends) is not buried.

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?

Annotations cover the mutation/safety profile and there is no output schema to explain, so the core is covered. Gaps remain: no guidance on the reason parameter or notes, and no statement about re-suppressing an already-suppressed address.

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 only 25% – just apiKey is documented. The description mentions only 'an email', leaving notes and the reason enum (bounce/complaint/unsubscribe/manual) completely unexplained in both schema and description, so it fails to compensate for the coverage gap.

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+resource ('Add an email to the suppression list') and adds the consequence ('future sends to this address will be blocked'), making it clearly distinct from remove_suppression and list_suppressions. It does not name a sibling explicitly, which keeps it just short of 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?

Usage is implied by the purpose: an agent can infer it is used to block an address. However, the description gives no explicit when-to-use criteria, no prerequisites (e.g., needing a verified workspace or API key), and no mention of the reason field that distinguishes bounce/complaint/unsubscribe/manual suppression.

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