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

With no annotations provided, the description discloses the tool's side effects: it's a non-mutating echo, requires x402 payment, and costs $0.01/call. It adds meaningful context beyond the schema, though it doesn't detail response format or failure behavior.

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?

Two sentences, front-loaded with the core action, followed by the diagnostic context and cost. No redundant 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?

As a simple diagnostic echo tool, the description covers purpose, cost, and behavioral context sufficiently. It doesn't specify the timestamp format, but that's a minor detail for an echo endpoint.

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?

The schema has zero defined properties but allows arbitrary query parameters with a clear description. The tool's description reinforces that query parameters are returned verbatim, and since parameters are free-form, there is little more to explain.

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 echoes request query parameters back with a timestamp, and identifies it as an x402 client diagnostic. This specific verb+resource makes it distinct from the sibling analysis 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?

It conveys a diagnostic use case ('exercises the payment headers, not just the HTTP client') and mentions cost, implying it's for testing x402 integration. However, it doesn't explicitly state when not to use it or name an alternative, but given the sibling set, the context is sufficient.

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