pay

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

With no annotations, the description carries the full burden for behavioral disclosure. It clearly states the tool signs an authorization and returns a header value, which is valuable. However, it does not disclose whether the signing has side effects (e.g., funds movement), any permission requirements, or failure modes. The description adds some context but is not comprehensive.

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 two sentences long, front-loaded with the purpose, and contains no fluff. Every word adds value, making it highly concise and well-structured.

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 tool is moderately complex with 4 parameters and no output schema. The description explains the return value ('header value') but lacks broader context such as prerequisite steps (e.g., obtaining a 402 challenge), how this fits into the x402 flow, or example usage. It is adequate but has gaps.

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?

All four parameters are described in the input schema (100% coverage), so the schema fully documents them. The description does not add any extra parameter semantics beyond what the schema already provides, making the baseline score of 3 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 signs an x402 payment authorization for a USDC transfer on Hedera, which is a specific verb ('sign'), resource ('x402 payment authorization'), and scope ('USDC transfer on Hedera'). This distinguishes it from sibling tools like transfer_usdc (actual transfer) and x402_fetch (likely fetching challenges).

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 context by mentioning the returned header should be attached when retrying the paid request, but it does not explicitly state when to use this tool versus alternatives like transfer_usdc or x402_fetch. No exclusions or alternatives are provided, leaving the when-to-use decision to inference.

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