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

Adds real behavioral context beyond the annotations: server-side snapshot persistence and update, wallet-scoped privacy, and a per-call x402 cost. One caveat: saving/updating a snapshot is a stateful side effect while the annotation declares readOnlyHint=true — a mild tension worth noting, though it likely refers to non-destruction of external resources rather than internal cache writes.

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?

Three tightly packed sentences, front-loaded with the core behavior, then state semantics, then privacy and cost. No filler; the parenthetical '(lines added and removed)' and '(x402)' are dense but each carries information.

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 usefully sketches the return content (added/removed lines) and the first-call-vs-later-call distinction. It leaves open what the first call returns and failure modes (unreachable page, changed content type), which is a minor gap for a one-parameter tool.

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 0% for the single url parameter. The description implies it is the page to watch but adds no format details (normalization, scheme handling, query strings). With only one obvious parameter this is adequate but not enriching.

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 concrete verb+resource (reports page changes since last check, lines added/removed) and makes the stateful watch semantics explicit. It is clearly distinguishable from scrape/crawl siblings, though it does not name any of them for contrast.

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?

Explains the operating model: first call creates the snapshot, subsequent calls diff and update it, which tells the agent when and how to invoke it iteratively. It stops short of naming alternatives (e.g. since, text_diff, crawl) or stating when not to use it.

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