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

With no annotations, the description carries the full burden. It discloses the payment flow, the requirement to send the exact amount, and the need to call purchase_status. It also mentions a billing condition. However, it does not mention any state changes, idempotency, expiration, or the user_confirmed parameter, leaving gaps in behavioral expectations.

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 concise, with two sentences in English and Korean. It front-loads the primary action and provides the next step and a conditional. It is well-structured and efficient, though it could be slightly more streamlined by removing the bilingual duplication.

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 5 parameters (4 required), no output schema, and no annotations, the description is incomplete. It explains the payment flow and billing condition but omits the meaning of plan_code, email, and agent_id, and does not describe the response format beyond mentioning the USDT amount and address. It also fails to mention the user_confirmed requirement from the schema.

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 only 40%, and the description only addresses the billing parameter (with the annual condition). It does not explain plan_code, email, or agent_id, which are required but have no schema descriptions. The description adds some value for billing but fails to compensate for the missing coverage of three critical parameters.

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 the tool's purpose: 'Open a payment for a plan' and explains it returns a unique USDT amount and address. It differentiates from sibling purchase_status by explicitly describing the next step after payment, and the name itself distinguishes it from purchase_quote. The verb+resource is specific.

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 gives a clear workflow: open payment, send exact amount, then call purchase_status to confirm. It also provides a conditional for using billing='annual' for plans under the network minimum. However, it does not explicitly contrast with purchase_quote or state when not to use this tool, so it falls short of full guidance.

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