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

With no annotations, the description carries the full burden and does well: it discloses the redirect policy, the HEAD-then-GET fallback strategy, and the payment requirement across three rails (x402, Cashu NUT-24, L402), which is critical operational context. It omits error behavior, timeouts, and return format, but the payment and request-mechanics disclosure is genuinely useful.

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 front-loaded sentences: the capability comes first, followed by request mechanics and pricing. The payment enumeration is verbose but each item is functionally necessary since no other field conveys cost.

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 single-parameter fetch tool with no output schema or annotations, the description covers what is returned and the payment requirement, but leaves error handling, timeout behavior, and result formatting unaddressed. Adequate but with clear gaps an agent would want filled.

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 one required 'url' parameter with 0% schema description coverage, and the description adds no meaning beyond 'for a URL' — it never says whether a scheme is required, whether non-HTTP schemes work, or what format is expected. The single parameter is left essentially undocumented in both places.

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?

States a specific resource and output set ('HTTP response headers, status and timing for a URL'), which is clearly distinct from siblings like ssl, meta, and site_audit. It does not explicitly name a sibling to distinguish against, but the scope is unambiguous enough to route correctly.

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?

No when-to-use guidance or named alternatives are given; the agent must infer that this tool is for inspecting raw HTTP response metadata. The behavior notes ('no redirect following, HEAD then GET fallback') describe how it runs, not when to pick it over site_audit or ssl.

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