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

Annotations already mark this as a non-readOnly, destructive, idempotent operation. The description adds valuable behavior beyond that: approval is required, delivery is deferred until the inbound call artifact is ready, and saving settings alone is not delivery proof. No contradiction with annotations.

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 the most important approval-gating note and no filler. Each sentence adds a distinct fact: what is saved, when delivery starts, and what does not count as delivery proof.

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 and an output schema present, the description covers the essential non-obvious semantics: approval, exact session scoping, async delivery trigger, and the delivery-proof caveat. It does not spell out every parameter, but the remaining gap is modest for a 6-parameter mutation with a rich schema.

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 0%, so the description must carry parameter meaning. It explains channel (sms/email) and destination, and partially covers activation_session_id via 'exact active activation session,' but it does not clarify idempotency_key, business_id, or the authority object.

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 and resource: 'Save the owner-approved SMS or email destination for the exact active activation session.' This clearly identifies what is being persisted and scopes it to a single session, distinguishing it from notification retry, sending, or alert configuration tools.

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 context: this is approval-gated and should be used to set the destination for the active session, not as proof of delivery. It does not explicitly name sibling alternatives such as retry_activation_notification or list when-not-to-use conditions, so it stops short of a 5.

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