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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses the payment model (x402, $0.002 USDC on Base/Solana/Arc), that failed calls are free, and hard result caps (500 captures, 200 added/removed diff lines). These are exactly the operational facts an agent needs before calling.

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 capability, then caveats, then price; every clause carries information. It is a dense single long sentence chain with no whitespace/breaks, which slightly hurts scannability but wastes no words.

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 an output schema present, return values need not be described, and the description still covers capabilities, per-mode behavior, limits, rendering caveats and cost. Nothing material for correct invocation is missing.

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 coverage is 100%, so the baseline is 3, but the description goes further by explaining what each mode returns (per-day captures vs. added/removed lines, the default of captures) and that the date params drive closest-vs-range behavior. This adds semantic meaning over the terse schema strings.

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 names a concrete verb+resource ('Wayback Machine snapshots of a public URL') and enumerates the four query shapes (closest-to-date, range list, first/last, diff). It is unambiguous what the tool does, but it never distinguishes itself from plausible siblings like pagespeed, sitemap, redirects or text_diff.

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 implied by mode descriptions ('diff ... compares the latest snapshot's text with the live page'), and the JS-rendering caveat hints when diff is inappropriate, but there is no explicit 'use this when... instead of X' guidance. The agent must infer that diff replaces a separate comparison tool.

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