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

The description goes beyond annotations by explaining the payment flow (x402 paywall, direct wallet payment) and the return payload (listing and paid_endpoint). It suggests both create and update behavior, which aligns with the idempotentHint, but does not detail side effects like overwriting existing entries.

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 compact and well-structured, with two clear sentences covering the operation, endpoint, payload, and return values. It front-loads the primary action and avoids unnecessary elaboration.

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?

The description provides sufficient context for using the tool, including the endpoint, required parameters, and return values. It mentions the seller must be registered, which covers a key prerequisite, but does not discuss error scenarios or idempotency details (though annotations cover idempotency).

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 description restates the parameter list from the schema but adds minimal new meaning. The schema already provides per-parameter descriptions (e.g., 'Price per call'), so the tool description adds little semantic enhancement beyond contextualizing them as part of a paid listing.

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 creates or updates a paid listing for a registered seller, specifying the exact endpoint and required parameters. It is specific to listing management and distinguishable from sibling tools like registering a seller or querying services.

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 indicates the tool is for creating or updating listings but does not explicitly discuss when to use it versus alternatives, such as when a seller needs to be registered first or when a read-only operation is preferred. It implies prerequisites but does not state them as usage guidelines.

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