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

With no annotations, the description carries the full burden. It usefully discloses that both daily caps apply, that Stripe/resident-wallet purchases are excluded, and that the item goes 'into your account,' but it omits irreversibility, actual cost/currency deduction, failure behavior when caps are hit, and idempotency semantics.

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 a single front-loaded sentence with semicolon-separated constraints and no filler. The phrase 'both daily caps apply' is slightly ambiguous, but overall it is efficient.

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 purchase mutation with no annotations, no output schema, and 0% parameter description coverage, the description omits several operationally important details: what is deducted, whether the purchase is reversible, what happens on cap exhaustion, and what the requestId protects against.

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 names itemSlug and requestId, but only repeats that requestId is a required UUID and does not explain its likely idempotency role, nor where itemSlug comes from or its format beyond the schema's length bounds.

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: 'Buy one operator-scoped Legend's Locker item by itemSlug into your account.' This clearly distinguishes it from generic buy/buy_ingredient and from Stripe/wallet purchases, though it does not explicitly name locker_catalog or other siblings.

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 use for locker-item purchases and excludes Stripe/resident-wallet purchase contexts, but gives no explicit when-to-use guidance versus siblings like locker_catalog, locker_inventory, buy, or buy_ingredient.

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