Compare Pages or a Stored Baseline

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

Beyond the destructiveHint annotation, the description discloses that baseline mode records the first call, warns to rely on guaranteed deltas rather than medians alone, and states that replaceBaseline overwrites local baseline state. This is meaningful behavioral transparency beyond what annotations 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?

Three sentences with no wasted words: the first states the core purpose, the second gives operational guidance, and the third provides examples and the destructive state-change warning. The structure is front-loaded and easy to parse.

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 an 8-parameter tool with full schema descriptions and an output schema, the description covers the key operational nuances: mode selection, first-call baseline behavior, run counts, examples, and state overwriting. Nothing critical for correct invocation 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 coverage is 100%, so the baseline is 3. The description adds value by explaining the behavioral semantics of baseline mode's first call and why runs=3 or more is recommended, rather than merely repeating schema defaults.

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 opens with a specific verb and resource: 'Compare two pages now' or 'measure one page against its locally stored baseline.' It clearly distinguishes the two modes and gives concrete examples, making the tool's purpose distinct from sibling tools like pagespeed_analyze_page.

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 explains when to use pages versus baseline mode and provides practical examples such as comparing staging against production or verifying a deployed fix. It does not explicitly name sibling alternatives or exclusions, but the contexts are clear enough to route an agent correctly.

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