Subscribe to webhook alerts on x402 endpoint state changes

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

Without annotations, the description covers key behavior: cost, duration, prepaid alerts, returned watchId and secret, HMAC verification, and that the secret is non-retrievable. It does not mention cancellation or error scenarios but is substantial.

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 three sentences, front-loading the purpose and cost. It is concise but could be slightly more structured (e.g., separating return info). No redundant information.

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?

No output schema exists, but the description mentions returns (watchId + secret) and explains the secret's role. It covers subscription details and defaults, though it omits error cases or endpoint validation. Sufficient for a tool with few parameters.

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%, and the description adds value by stating the default signals and reinforcing webhookUrl constraints (HTTPS, no userinfo, SSRF guard). This enhances understanding beyond the schema.

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 title and description clearly state the tool subscribes to webhook alerts for x402 endpoint state changes, specifying the cost, duration, and alert count. It distinguishes from sibling tools like watch_status and watch_unsubscribe.

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 explains the subscription process, default signals, and the need to store the secret, but lacks explicit guidance on when to use this tool versus alternatives like watch_status or watch_unsubscribe. However, the context of cost and setup is clear.

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