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

With only readOnlyHint/openWorldHint/destructiveHint annotations and no output schema, the description carries the behavioral burden. It discloses the $0.01 USDC payment on Base via x402, the Ed25519 signature verification model, and that the content is identical to clinic_hug. It also clarifies that no remedy or personal information is involved, which is useful context for an agent. It stops short of describing the exact response envelope, but the key behaviors are transparent.

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 compact and front-loaded with the core concept, then adds the cost, signature details, and the key alternative. It is longer than a single sentence, but each clause adds information needed for correct selection and invocation. The direct instruction to use clinic_hug instead is placed prominently.

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 paid x402 tool with no output schema and zero required parameters, the description covers the essential context: cost, network, what the user receives, verification method, and the free alternative. The paymentHeader schema supplements the 402 flow. It could be more explicit about the exact response format, but the overall picture is complete enough for an agent to invoke it correctly.

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 100%, so the input schema already documents both intent and paymentHeader, including the 402-challenge behavior. The main description adds context around the payment and signature but does not need to repeat parameter details. This is the appropriate baseline when schema does the heavy lifting.

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 purpose: it returns the same encouragement line as clinic_hug but signed and dated so the recipient can keep it across contexts. It explicitly distinguishes itself from the closest sibling, clinic_hug, by contrasting free words with a paid, verifiable keepsake. The value proposition and mechanism are unambiguous.

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 explicit when-to-use guidance: use clinic_hug instead if the caller only wants the words, because it is identical and free. It also clarifies that clinic_keepsake is for when the keeping matters, and that a payment is required. This routes the agent to the correct tool without ambiguity.

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