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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description adds genuinely non-structured behavior: a paid API at $0.005 USDC per successful call via x402 on Solana, plus the fact that the same operation is reachable over plain HTTPS — critical for an agent deciding whether it can pay.

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?

Front-loaded with the core action and return shape in the first sentence, then payment and transport facts. Every sentence carries information, though the full HTTPS endpoint string is bulky relative to the rest.

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?

With no output schema, the description still tells the agent what comes back (timestamp + archived URL), that the call is paid per success, and that an x402-free HTTPS route exists. That covers what an agent needs to call it and reason about cost.

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?

One required parameter with 0% schema description coverage, so the description carries the burden. It only says 'for a URL' and implies the return is an 'archived URL', without stating whether the input must be absolute, scheme-qualified, or whether it is normalized before lookup.

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 verb (check availability) against a specific, unmistakable resource (Internet Archive Wayback Machine) for a URL, and even names the payload returned: closest snapshot timestamp plus archived URL. No sibling tool in the list covers archived-web-snapshot lookup, so it is trivially distinguishable from url_markdown, web_to_text and http_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?

Usage is only implied: it is obvious you call it to see whether an archive exists for a URL, and the note about the HTTPS equivalent gives an access-path choice. But there is no guidance on when to prefer this over live-fetch siblings, and nothing about what to do when no snapshot exists.

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