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

With no annotations, the description carries the burden and discloses the non-obvious multi-call protocol and that the first call is expected to return a 402 challenge rather than complete a payment. It stops short of explaining side effects, idempotency, or authentication-related behavior.

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 tightly packed sentences with no filler: the first states the operation, the second gives the exact call sequence. It is front-loaded and every phrase earns its place.

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?

There is no output schema and no annotations, so the description must explain the full workflow. It covers only the challenge/sign/submit loop and omits what the second call returns, where relayPaymentId comes from, and how to handle failure or status via get_x402_relay_status or retry_x402_relay_payment.

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 description coverage is only 33%, and the description compensates only for paymentSignature by mentioning the encoded signature. relayPaymentId and apiKey remain unexplained, and the source of relayPaymentId from a previous quote is left to inference.

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 action ('Submit an x402 PAYMENT-SIGNATURE for a relay quote') and reveals the two-phase challenge flow. It is clearly distinct from create_x402_relay_quote and get_x402_relay_status, though it does not explicitly differentiate from retry_x402_relay_payment.

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?

It gives explicit sequencing: call first without paymentSignature to receive the 402 challenge, sign it, then call again with the signature. This is clear usage context, but it never names sibling alternatives such as retry_x402_relay_payment or get_x402_relay_status for failure and status cases.

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