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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds a genuine behavioral caveat not in annotations: for localhost/staging-behind-login pages the server-HTML comparison is skipped. It does not describe the return value, though an output schema exists.

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?

Single sentence, front-loaded with the core action before the parenthetical checklist, and the non-public-page caveat is a clean second sentence. The long inline list of checks is dense but each item is informative; slight bloat keeps it from a 5.

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 analysis tool with full annotation coverage and an output schema, the description is nearly complete: it explains inputs' provenance, checks performed, and the non-public-page caveat. Nothing critical for correct invocation is missing, though the absence of result-format framing is a minor gap.

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%, so url, results and the optional no_js probe are already documented with examples. The description only alludes to 'probe result' generically and adds no format, ordering, or per-viewport semantics beyond the schema. Baseline 3 is appropriate.

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 (analyse) and resource (the layout probe results) and explicitly positions itself against siblings: it consumes get_layout_probe output and runs 'the same checks as render_page' plus a server-HTML comparison. An agent can distinguish it from render_page/get_layout_probe without opening a schema.

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 makes clear this operates on get_layout_probe output 'measured in your own browser' and states one exclusion (non-public pages skip the server-HTML comparison). It does not name a competing tool or say when NOT to use this versus render_page, so it stops short of explicit routing.

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