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

With no annotations, the description carries the burden and discloses key behavior: it is paid at $0.01 USDC/call via x402 on eip155:8453, performs a handshake, and explicitly does not make a tool call. It still omits rate limits, error behavior, and whether payment must be settled before the handshake, but the main behavioral traits are covered.

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 a single, dense sentence that front-loads payment metadata and then states the operation and return details. It is efficient and contains no filler, though the bracketed payment prefix makes it slightly less immediately purpose-focused.

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?

There is no output schema, but the description enumerates the key return values (reachability, protocol version, tools, schemas, latency, OAuth metadata) and covers the payment model. It is mostly complete for an endpoint probe, missing only finer details like timeout behavior or the exact payment flow.

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?

There is only one parameter, and the input schema already documents it fully with an example endpoint. The description adds no additional meaning about the URL parameter, so the high schema coverage sets the baseline at 3.

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 states a specific operation: performing a real MCP Streamable HTTP handshake (initialize + tools/list, no tool call) and returning reachability, protocol version, tools, schemas, latency, and OAuth metadata. It clearly distinguishes its scope from tools that actually invoke MCP tools via the 'no tool call' phrase, though it does not explicitly name sibling alternatives like x402_probe.

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 lists what the probe returns, which implies it is for endpoint inspection, but it provides no explicit when-to-use guidance, no exclusions, and no comparison to sibling tools such as x402_probe. It also does not state prerequisites like payment requirements before invocation.

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