Check x402 Payment Intent Against Policy

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

No annotations are provided, so the description carries the behavioral burden. It discloses the evaluation criteria and that the cap is shared with trade intents, and 'before signing or sending' implies a preflight check. However, it does not state whether the call has side effects, what the result/verdict looks like, or how policy violations are returned.

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?

Two sentences with no wasted words: the first states the core behavior, the second provides actionable timing. The structure is front-loaded and easy to parse.

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?

Given no output schema and no annotations, the description omits important return semantics: what does the check return when the payment is allowed versus blocked? It also does not explicitly confirm non-mutation. The shared-cap note and timing are helpful, but an agent still cannot fully anticipate the tool's response or failure behavior.

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 100%, so the parameters are already documented in the schema. The description reinforces that usdValue is checked against the caps and resourceUrl identifies the x402 resource, but it adds no new format, unit, or constraint details beyond the schema. Baseline 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 states a specific verb and resource: it 'evaluates a proposed x402 protocol payment' against identified spend caps. It also notes the caps are shared with trade intents, which helps position it relative to the sibling, though it does not explicitly contrast the two tools.

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 an explicit call timing: 'Call this BEFORE signing or sending any x402 payment.' This is clear contextual guidance, though it does not explicitly state when to use check_trade_intent instead.

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