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 dynamic pricing model (amount + 0.01 fee), the transfer of the exact requested amount, and the auto-detection mechanism. This is substantial behavioral context, though it doesn't mention risks or error handling.

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 (three sentences) and front-loaded with the purpose. The pricing and example are useful and every sentence contributes value. No 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 single-parameter tool with no output schema, the description is fairly complete. It explains what will be transferred, the fee structure, and provides an example. Missing some edge-case behavior, but overall sufficient for a straightforward funding operation.

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 input schema already describes the 'amount' parameter with full coverage, including the fee. The main description adds an example but doesn't introduce new parameter meaning beyond what the schema provides. Baseline of 3 is appropriate.

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 function: 'Fund your custodial wallet with USDC.' This is a specific verb and resource, and it differentiates from the sibling tool 'fund_wallet_eth' by specifying the currency (USDC).

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 provides clear context for when to use the tool, including an example and the requirement that the owner wallet is auto-detected from x402 payment. It doesn't explicitly mention alternatives or exclusions, but the USDC-specific wording makes the intended use unambiguous.

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