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

Beyond the readOnlyHint/openWorldHint annotations, it discloses how caching is decided (HTTP ETag/Last-Modified), that no state is stored server-side and the fingerprint lives with the agent, and the billing model (charged only on success, US$0.001 per call, API key credits or x402). These are exactly the operational facts the agent needs and that the annotations do not provide.

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?

Well front-loaded: the use case comes first, then the mechanics, then the billing note. It is efficient overall, though 'Saves tokens on every re-check' restates the opening premise and reads as light marketing.

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 documents the return shape — sections plus fingerprint on the first call, changed sections and removed headings on subsequent calls, or changed:false. Combined with the annotation coverage of the read-only profile and the explicit billing terms, an agent has everything needed to call it correctly.

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 only 25%, so the description must compensate. It fully explains 'previous' semantics — send back the fingerprint from the prior call, omit on first call, and what comes back (changed sections, removed headings, changed:false). The 'engine' enum values and 'user_agent' are left completely unexplained in both schema and description, which keeps this from a 5.

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 concretely explains the two-call delta workflow: the first call returns sections plus a fingerprint, and re-calls return only changed sections. This goes well beyond the name 'delta' and makes the resource and operation unambiguous. It doesn't name the sibling tool (e.g. 'read') as the one-off alternative, so the differentiation is implied rather than stated.

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?

'For pages an agent checks again and again' clearly signals the usage context on the first call and implies that one-off fetches belong elsewhere. What's missing is an explicit exclusion or named alternative such as the 'read' sibling for single fetches.

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