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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds genuine behavioral context beyond that: issues are reported with stable codes and the exact fields diffed (title, description, H1, canonical, robots, structured data, word count).

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?

Two sentences, no filler, with the core action and scope front-loaded and the usage trigger placed last. Every clause carries information the agent can act on.

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?

An output schema exists so return values need not be spelled out, yet the description still summarizes what comes back, and it covers inputs, use case, and safety context. Nothing needed to call it correctly 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 description coverage is 100% and all three parameters (url, before, after) are documented in the schema itself. The description only restates the before/after relationship already implied by the param names, adding no syntax, format, or constraint details 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?

States a specific verb (compare) and resource (two versions of a page's HTML, e.g. before/after a code change) and scopes the output (SEO score, issues fixed/introduced, field-level changes). The 'two versions of the same page' framing distinguishes it from the sibling compare_pages, which implies comparing distinct pages.

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?

Gives a concrete usage scenario ('use it in code review to catch SEO regressions before they ship'), which tells the agent when this tool belongs in a workflow. It stops short of explicitly contrasting with compare_pages or rescan_and_compare, so the choice between near-neighbors is left to inference.

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