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

With no annotations, the description carries the full burden and excels: it discloses stackability ('each call pushes expires_at 30 min further'), a cap ('up to 24h total lease'), ownership restriction, unrecoverable expiration, and the exact cost (0.20 USDC) and payment mechanism. This is comprehensive behavioral disclosure.

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 two concise sentences, front-loaded with the primary action. Every clause adds a specific constraint, behavior, or cost—no filler or redundancy.

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?

Given this is a simple extension operation with two params and no output schema, the description provides all necessary context: what it does, how accumulation works, exceptions (expired), alternative path, and cost. The agent has enough to decide when and how to invoke it.

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?

The input schema already provides 100% coverage of both parameters, so the baseline is 3. The description adds context that number_id is a lease id from phone_temp_number, but does not add significant parameter-level semantics beyond what the schema already states.

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 clearly states the action ('Rent another 30 minutes') and resource ('live disposable temp number'), and explicitly contrasts with a fresh lease via phone_temp_number, distinguishing it from the sibling tool.

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 provides clear usage context: 'Owner-only' indicates who can use it, and 'expired temp leases cannot be revived (lease a fresh one via phone_temp_number)' gives an explicit when-not case and alternative. It also mentions the payment method (x402) for each action.

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