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

Goes well beyond the annotations with statelessness ('nothing stored'), SSRF guarding, output truncation (added lines up to 20 plus counts), billing behavior (changed:false is charged, bad input/blocked/upstream errors are not), price and payment rail, and a warning that returned content is untrusted third-party data. These are exactly the non-obvious traits an agent needs before invoking a paid, open-world tool.

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-loads purpose and call mechanics in the first two clauses; the remaining sentences each carry distinct operational facts. The payment/terms tail is dense but not redundant.

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?

No output schema exists, yet the description specifies the return shape (changed boolean, added lines, added/removed counts), the truncation limit, and the failure/charging semantics. An agent has everything needed to call and interpret results.

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 parameters are already documented; the description still reinforces the `since` token's role as state carried from the prior answer and the omit-on-first-call rule. Baseline 3 is exceeded only slightly since it largely restates the schema.

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?

Names a specific verb and resource: detects whether a public page/endpoint changed since a prior check. It is functionally distinguishable from fetch/screenshot/http siblings by the change-detection framing, but it never names an alternative tool, so the differentiation is left implicit.

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 call pattern clearly: GET the url, pass `since` from the previous answer, omit it on the first check. That gives solid context for correct sequencing but offers no explicit exclusions or named alternatives for when a plain fetch would be better.

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