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

With no annotations, the description carries the full burden. It discloses key behavior: deposit_usd and withdraw_usd move USDC from the prepaid balance, and the daily job renews 1 year at ≤30 days if the vault covers the price, otherwise sending reminders at 30/14/7/1 days. It also states ownership requirement, leaving only edge cases like simultaneous deposit/withdraw or failure modes unaddressed.

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 sentences with zero waste. The core purpose is front-loaded, followed by vault mechanics and renewal automation, each sentence earning its place.

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 mutation tool with no annotations and no output schema, the description provides the essential context: ownership prerequisite, fund flow between prepaid balance and vault, and the renewal schedule. It omits return value details and failure conditions, but covers enough 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 description coverage is 0%, so the description must compensate. It clearly defines deposit_usd (moves USDC from topup_balance into the domain's vault) and withdraw_usd (moves it back), and implies enabled via 'turn auto-renew on/off'. The domain parameter is obvious from the purpose. However, it does not clarify whether deposit_usd and withdraw_usd can be used together or what happens if enabled is omitted.

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 a specific verb and resource: toggle auto-renew for a domain and fund/withdraw its renewal vault. It distinguishes this from sibling tools like renew_domain (immediate renewal) and topup_balance (prepaid balance top-up) by explaining the vault mechanics.

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?

The description implies when to use the tool (to enable auto-renew or manage the vault) but does not explicitly name alternatives such as renew_domain for immediate renewal or get_renewal_balance for checking balance. The daily-job behavior gives useful context but no explicit exclusion guidance.

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