Preview or send bulk SMS

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

Annotations already declare destructiveHint=true, readOnlyHint=false and non-idempotency, but the description adds genuinely new context: messages are billable, server-side policy gates still apply, user approval is required, retries are forbidden, and dry-run output is not a price quote. That is exactly the operational detail an agent needs before firing a destructive action.

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 tight sentences, each earning its place, with the default behavior front-loaded ahead of the escalation condition and the dry-run caveat last. No filler.

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?

Covers billing, approval, gating and retry policy for a destructive write tool with no output schema; the schema handles recipient/message constraints. It could say more about partial-batch failure behavior, but it is complete enough to invoke correctly.

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% (dryRun and senderId are documented; recipients and message are not), so the schema does not carry the full load. The description clarifies dryRun's intent and the approvals it implies, but adds nothing about recipient format, batch size, or message constraints.

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 set (validate/preview/send) against a concrete resource (SMS) and immediately disambiguates the default mode from the sending mode. An agent can tell this is the messaging tool and not the airtime sibling without opening the schema.

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?

Gives the exact condition that escalates to a real send (dryRun=false with server gates enabled) and an explicit human-approval prerequisite plus a no-auto-retry rule. It stops short of naming alternative tools such as at_send_airtime, so it earns a 4 rather than a 5.

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