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

Annotations say the tool is not read-only, not idempotent, and not destructive, but the description adds meaningful behavioral context: it does not sign or execute payment, and it requires the caller to assess whether their mandate allows the transaction. This goes beyond annotation alone and clarifies what side effects are intentionally absent.

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 short sentences with no filler. The core action and amount constraint are front-loaded, followed by a critical non-execution disclaimer. Every sentence carries information the agent needs.

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?

While the output schema covers return values and annotations provide some safety context, the description is incomplete for a 9-parameter tool. It leaves the focus enum and most optional parameters unexplained, and it does not describe the intended campaign context or how the returned URL should be handled. The agent can call it minimally but cannot reliably make informed choices about all inputs.

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 0% and there are 9 parameters, yet the description only explains the amount_usdc minimum ('0.01 upward'). It does not clarify focus enum values, message constraints, supporter fields, idempotency_key requirements, reach_receipt_id, public_recognition, or champion_profile_id. The description fails to compensate for the absent schema documentation.

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 uses a specific verb/outcome: choose a USDC amount and receive an exact x402 payment URL. It also distinguishes itself from execution tools by stating it 'prepares but does not sign or execute payment.' This is clear and lets an agent know exactly what this tool produces versus a payment-execution sibling.

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 useful context—this prepares rather than executes a payment—and cautions to only authorize if the mandate permits. However, it never names alternative tools or explicitly states when to prefer this tool over siblings like accept_relay or create_relay, leaving some routing to inference.

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