pay_invoice

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

No annotations are provided, so the description carries the full burden. It discloses that it initiates a payment and returns a checkout URL, offering some insight into the flow. However, it does not mention side effects like whether the invoice is locked, payment reversibility, or prerequisites beyond ownership and unpaid status.

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 sentence with no unnecessary words. It front-loads the action and concisely states the action, subject, and result.

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 tool with one parameter and no output schema, the description provides adequate context: it states the core action, a prerequisite condition, and the return value. It omits details about error conditions or post-payment behavior, which could be relevant for a financial operation, but the essentials are covered.

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 schema describes invoice_id as 'Invoice id to pay' (100% coverage). The description adds the constraint that the invoice must be owned and unpaid, providing additional meaning beyond the schema's simple field description.

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 uses a specific verb 'Initiate' and a clear resource 'crypto payment for an owned unpaid invoice', and explicitly mentions the output 'returns a checkout URL'. This clearly distinguishes it from sibling tools like topup_balance.

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 usage for paying owned unpaid invoices but provides no explicit when-to-use guidance or alternatives. It does not explain when to choose this tool over topup_balance or other payment methods.

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