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

Even though annotations already declare openWorldHint true and readOnly false, the description adds critical behavioral detail: unsigned calls return a live x402 challenge, never auto-spend, and require a challenge-specific payment_signature to proceed. This goes beyond the annotations by explaining the payment negotiation flow and the meaning of the payment_signature parameter.

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 dense sentences, zero filler. The primary function is stated first, followed by the payment flow caveat. Every word earns its place, and the critical behavioral nuance is not buried.

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?

For a 3-parameter tool with no output schema, the description conveys the essential invocation flow: URL in, Markdown out, optional max_chars, and the payment challenge handshake. It does not enumerate error cases or exact response schema, but the description provides enough to attempt a correct first call.

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 description coverage is 67%: url and payment_signature have descriptions, while max_chars does not. The main description adds context for payment_signature ('challenge-specific') but does not clarify max_chars beyond the schema's absence. This is adequate but not exceptional; the schema and description together cover most 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?

The description states a specific action (give one public HTTPS URL, receive Markdown) and a specific resource (public HTTPS URLs via Clean Web Reader). It clearly differentiates the tool from the sibling capability and x402 tools, which are about metadata/contracts rather than fetching web content.

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 makes usage context clear: use this tool to read a public HTTPS URL into LLM-ready Markdown without an SML account. It also provides procedural guidance for the x402 flow (unsigned call first, then retry with a challenge-specific signature). It does not explicitly name alternatives or when-not-to-use, but that is not needed given sibling differentiation.

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