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

Annotations already declare destructiveHint=true and idempotentHint=false. Beyond that, the description adds a real precondition ("Turning a source on needs a statement of where those people agreed") and a precedence rule ("unsubscribes and suppressions always win"). It does not mention required permissions or partial-failure behavior, so it is solid but not exhaustive.

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 with the action front-loaded, followed by the precondition and then the scope limits. No filler, though the third sentence slightly overlaps the second in framing scope.

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 destructive, non-idempotent mutation with no output schema and only partial parameter documentation, the description covers the essential unknowns: what it changes (new contacts only), the precondition for enabling a source, and that suppression/unsubscribe state overrides it. Missing authorization details keep it from a 5.

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 50%, so the description partly carries the load: "consent model or a source default" maps the two top-level parameters, and "a statement of where those people agreed" explains the nested source field. But it does not clarify the enabled/source pairing or the per-source enable semantics beyond what the schema already states, so it lands at the baseline.

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: "Change the consent model or a source default for new contacts." The "for new contacts" scoping implicitly separates it from per-contact tools like set_contact_consent, but no sibling is named explicitly, so it falls 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?

The description scopes usage ("applies to new contacts only") and notes precedence ("unsubscribes and suppressions always win"), which implies when it matters. However, it never names an alternative or states when NOT to use it versus get_consent_settings or set_contact_consent, leaving the selection reasoning to inference.

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