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

With no annotations, the description carries full burden and excels: it discloses non-custodial nature, exact return elements (coin amount, rate lock, wallet URI, pay page URL), the signed invoice_paid webhook, and the flat ~$0.02 fee debited from the watch credit meter. It also explains how amount tagging differs between Monero and Zcash.

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 dense but every sentence contributes: purpose, endpoint/return payload, webhook/fee behavior, and authentication options. It is front-loaded with the core action and remains readable despite its length.

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?

Despite having no output schema, the description adequately covers what the tool returns, how the payment flow works, what triggers the webhook, and what costs are incurred. It also explains the two authentication modes and where each is appropriate, making the tool fully actionable.

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%, but the description adds significant meaning beyond field names: it explains that amountUsdCents is converted at a locked rate, TTL locks the exchange rate, checkoutKey is a restricted client-safe key minted via POST /v1/checkout/keys, and that orderId is echoed on invoice, pay page, and webhooks.

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 opens with 'Accept an XMR/ZEC payment INTO YOUR OWN WALLET: creates a checkout invoice', using a specific verb and resource. It clearly distinguishes this creation tool from the sibling status/inquiry tools by naming the exact POST endpoint and the invoice-creation action.

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 gives clear context on when to use the tool ('Accept an XMR/ZEC payment...') and provides explicit guidance on authentication alternatives ('Use your watchId+watchToken server-side, or a restricted checkoutKey... anywhere you cannot keep secrets'). It does not explicitly say 'use checkout_invoice_status instead for status checks', but the create/status distinction is implicit from tool names.

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