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

With readOnlyHint already present, the description adds meaningful behavior context: the difference between directory mode and single-service mode, what include_services=true does to the payload size, and the explicit guarantee that no money fields are returned. This goes well beyond the annotations and helps the agent anticipate the response shape and scope.

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 dense but efficient, with every sentence earning its place: usage timing, mode behavior, and a safety/scope disclaimer. It front-loads the most important invocation guidance and avoids generic filler.

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?

Even without an output schema, the description tells the agent what to expect in both modes: status counts for the directory, and status/uptime windows/response time/consecutive failures/daily snapshots for a single service. It also addresses payload size and the absence of money fields, making it complete for a read-only health check tool.

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%, so the schema already documents all three parameters. The description adds value by clarifying mode-dependent behavior: no slug means directory snapshot, slug enables single-service detail, and include_services only applies in directory mode. This reinforces and extends the schema descriptions without redundancy.

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 names a specific verb and resource ('check x402 service health') and explains exactly what the tool does: tells whether a service is up right now. It also distinguishes the two operating modes (directory snapshot vs single service) and even notes what it does not return ('No money fields'), which separates it from sibling payment-related tools.

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 timing guidance: call before sending a payment or right after an unexpected failure. It does not name alternative sibling tools or say when not to use this tool, but the usage context is clear and actionable enough for an agent to know when to invoke it.

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