Diagnose a Page Performance Problem

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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, covering safety and side-effect expectations. The description adds a meaningful behavioral constraint: 'exactly one diagnostic lens' and 'Returns focused evidence rather than a full Lighthouse dump', which aligns with and enriches the annotation profile. No contradiction 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?

The description is three sentences of dense, useful information with zero fluff. It front-loads the core purpose, states the usage condition, and embeds a practical example in the same breath. Every sentence earns its place, making it highly efficient.

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?

Given that there is a full input schema, an output schema is present (per context), and annotations cover safety and idempotence, the description provides everything an agent needs to decide and invoke correctly: what it does, when to use it (vs. analyze), when not to, and a working example. Nothing essential 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%, so all four parameters are fully documented in the schema itself (baseline 3). The description adds value by providing a concrete example ('focus=render-blocking to identify CSS/JS delaying first render') that clarifies the practical meaning of the focus parameter beyond its enum listing, which justifies a 4.

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 ('Inspect') and resource ('one page') with a defined scope ('exactly one diagnostic lens'), and explicitly distinguishes itself from pagespeed_analyze_page by saying 'do not use it for a general score'. It also lists the available lenses, making the tool's purpose unambiguous and well-differentiated from siblings.

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?

The description gives explicit when-to-use guidance: 'Use after pagespeed_analyze_page identifies a problem' and when-not-to-use: 'do not use it for a general score'. It even provides a concrete example (focus=render-blocking) to illustrate proper invocation, which is more than most tool descriptions offer.

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