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

Annotations cover the safety profile (non-destructive, idempotent), and the description adds real substance beyond them: the three monitored conditions, that alerts arrive as a POST to webhook_url, and that the payload is a signed, logged attestation. Plan quotas (20 Pro / 200 Team) are also disclosed. It does not say what happens if the quota is exhausted or whether watches expire.

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?

A single dense sentence front-loads the plan requirement and then the watched resource, trigger conditions, and delivery mechanism. Every clause carries information; only the quota tail feels bolted on.

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?

With an output schema present, return values need no explanation, and the description still covers triggers, delivery channel, payload trust (signed attestation), and per-plan limits. Nothing an agent needs in order to call this correctly is missing.

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% and the schema already states 'give either id or url' and defines webhook_url as the alert receiver, so the description's 'by url or id' adds no new constraint. Baseline 3 is appropriate since the schema carries parameter meaning.

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?

Names a specific verb and resource ('watch an x402 endpoint or MCP server') plus the triggering events (down, back up, payTo/network change), so an agent knows exactly what the tool creates. It stops short of naming the sibling it contrasts with (check_service, check_artifact for one-shot checks), leaving the differentiation implicit.

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?

'Paid plans:' signals an eligibility prerequisite, which is useful gating context. However, there is no explicit statement of when to choose this over check_service or check_artifact (a polling check vs. a persistent webhook subscription), so the agent must infer the alternative from the trigger-based framing.

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