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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered structurally. The description's one contribution is warning that starting_after is an opaque cursor rather than an id, which prevents a real class of misuse, but it says nothing about result shape, ordering, or pagination termination.

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 short sentences, front-loaded with purpose before the returned-field facets and the cursor caveat. No filler, though the fragment style ("Who has opted out, on which channel, when, and how.") reads more as a spec gloss than a grammatical sentence.

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 six-parameter query tool with zero required params, a rich schema and full annotations, most burden is already carried elsewhere. What the description omits is any sense of the result shape or ordering implied by the cursor, and there is no output schema to compensate.

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 every parameter is already documented, including the enum semantics and the status/scope interaction. The description only reinforces the cursor meaning for starting_after, which the schema already states, 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?

The description opens with a specific verb+resource ("List opt-outs") and immediately enumerates the facets surfaced (who, channel, when, how), so the agent knows this is a read over the opt-out records. It does not explicitly distinguish itself from neighbors like list_blocked_users or list_contacts, which is the only reason it falls 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?

There is no statement of when to reach for this tool versus alternatives, no prerequisite or permission context, and no exclusions. The only practical routing hint is the note about starting_after, which is about invocation rather than tool selection.

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