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

Annotations already mark this as destructive and open-world, and the description adds critical context: this is a real action, not a preview, the message reaches the caller immediately, and it cannot be recalled. It also explains backend channel resolution and the need for explicit user confirmation.

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?

The description is front-loaded with the core action and then adds safety-critical details. It is appropriately sized for a destructive action, though some channel-switching guidance repeats what is already in the schema.

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, open-world tool with no output schema, the description covers the essential behavioral context: authorization source, channel resolution, message requirements, irreversibility, and confirmation. Nothing critical is missing for correct invocation.

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 coverage is 100%, so the schema already documents all three parameters in detail. The description adds useful semantics beyond the schema by explaining that EMAIL resolves from the contact's saved email and SMS resolves from the call's caller number.

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 and resource: send one EMAIL or SMS follow-up tied to an exact completed inbound call linked to a contact. It also distinguishes this from generic messaging by requiring an authorizing inbound call and contact linkage.

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 prerequisites (completed inbound call, linked contact) and a strong confirmation requirement before execution. It does not explicitly name alternatives such as sendSms or state when not to use this tool, so it falls short of full alternative routing guidance.

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