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

Annotations mark it non-read-only and open-world but say nothing about return shapes or workflow. The description goes well beyond them by documenting the two concrete return payloads (auto_approved false with approval_url vs. true with card/status), the follow-up call, and the auto-approval condition. That is exactly the behavioral context annotations cannot carry.

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?

Front-loaded with the core action, then the two return branches, then args. Slightly longer than minimal but each sentence explains a distinct branch or parameter; little waste.

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 non-idempotent, open-world payment-initiation tool with no output schema and no schema parameter descriptions, the definition supplies the return shapes, the workflow handoff, and all parameter semantics. Nothing essential for correct invocation is missing.

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 0%, so the description carries the full burden. It documents all four parameters including units for amount (major units, with a dollar example), the purpose of merchant, the exact shape of line_items, and the default for currency. This fully compensates for the missing schema descriptions.

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 (request approval to pay) and resource (purchase payment), and distinguishes itself from siblings by naming get_payment_result as the follow-up step. An agent can immediately tell this initiates a payment flow rather than recording or querying one.

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?

Explicitly describes both branches: the normal case where approval_url must be shown and then get_payment_result called, and the auto-approval case where the card is used directly. This is a complete when/how guide for this tool's role in the workflow.

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