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

With no annotations provided, the description carries the behavioral disclosure burden. It explains the underlying mechanism ('Sends a JSON-RPC tools/list request and verifies a valid response') and the return format, which is transparent about the operation. However, it does not reveal limitations such as potential timeouts or that 'spec-compliant' is based solely on tools/list, so it stops short of a 5.

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 four sentences, each adding value: purpose, method, usage guidance, and return value. It is front-loaded with the primary action and contains no filler or redundancy.

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?

Given the tool's simplicity (one parameter, no output schema, no annotations), the description is complete. It covers what the tool does, how it does it, when to use it, and what it returns, leaving no major gaps for an agent to invoke it correctly.

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 already provides 100% coverage of the single 'url' parameter, including a clear description. The tool description adds no extra parameter semantics beyond what the schema states, so the baseline of 3 is appropriate.

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's purpose: 'Actively probe any URL to check if it is a live, spec-compliant MCP server.' It uses a specific verb ('probe') and resource ('URL'), and the technical detail about sending a JSON-RPC tools/list request distinguishes it from generic URL checkers like check_url.

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 usage context: 'Use this before depending on a third-party MCP endpoint — manifests and documentation can claim MCP support without actually serving it.' This clearly indicates when to use the tool, though it does not name alternatives or state when not to use it, which would warrant a 5.

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