Compare two pages, or the same page before and after

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

Annotations already establish the read-only, idempotent, non-destructive profile. The description adds useful behavioral context by enumerating exactly what is compared and by explaining how to interpret the result. It does not contradict the annotations and does not need to repeat them.

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?

The description is compact and front-loaded: first sentence states the core function, second gives the primary use case, third provides an interpretation rule. Every sentence adds value with no superfluous detail.

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?

For a read-only comparison tool, the description covers what the tool does, when to use it, and what output dimensions to expect. It does not mention edge cases like unreachable URLs, but the annotations and simple three-parameter schema reduce the risk of mis-invocation.

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?

The schema already documents urlA and urlB with examples, and the description reinforces their semantic role as staging/production or before/after. However, timeoutMs is not explained in the description beyond schema constraints, and the description adds limited new parameter-level insight beyond 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?

The description states a specific verb and resource ('Check two URLs and report where they differ') and lists concrete comparison fields such as status, title, canonical, and byte size. The two-URL framing clearly distinguishes this tool from the sibling single-page and link-checking tools.

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?

It gives explicit use cases: comparing staging vs production and comparing the same URL before/after release. It also provides an interpretation rule for results ('did my deploy actually land?'), though it does not explicitly mention when to use a sibling tool instead.

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