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

Annotations only declare generic write/open-world/non-idempotent flags, but the description supplies the real behavioral payload: the $0.01 USDC cost on Base, the x402 payment rail, and critically that the user is only charged on delivery. The 48-hour reply SLA is also disclosed. This is exactly the context annotations cannot carry.

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 value proposition and destination are front-loaded, then cost, then gating, then the alternative — three tight sentences with no filler and every clause load-bearing.

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?

No output schema exists, yet the description still conveys the expected outcome (delivery, PRIORITY flag, 48-hour reply) and the payment semantics, so an agent knows what a successful call produces and what it costs. Nothing needed to invoke it correctly is missing.

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 baseline is 3, but the description adds a genuine constraint beyond the schema: the email must be the user's real address so Anto can reply, which affects which value an agent should pass. It says nothing about the optional 'company' field, so it stops short of a 5.

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 (send Anto a priority message) plus the concrete outcome (inbox flagged PRIORITY, reply within 48 hours). It also names the free sibling (book_call), so an agent can distinguish it from alternatives without opening any 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?

Explicit gating: 'Only call when the user explicitly asks to reach out and has approved the payment,' plus a required input condition ('use the user's real email') and a named alternative ('For a free option, use book_call'). Both when-to-use and when-not are covered.

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