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

The description goes far beyond the sparse annotations (readOnlyHint: false, destructiveHint: false). It discloses sandboxed iframe rendering, refusal of scripts/iframes/forms, size limits, design constraints, and that empty input clears to default. It also notes the auth and page claim requirement. No contradictions with annotations.

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 long but every sentence carries critical guidance. It front-loads the core purpose, then systematically covers design rules, constraints, and authentication. It's well-organized and free of filler.

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?

With one parameter and no output schema, the description provides everything an agent needs: what to write, constraints, design directives, clearing behavior, and auth requirements. There is no ambiguity about how to call it or what the result will be.

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 single parameter html is described in the schema as 'the cover HTML fragment', but the description adds substantial meaning: format constraints (self-contained, inline CSS, no scripts, ≤64KB), design guidance (narrow column, fluid units, light surface), and the clearing behavior. This enriches the schema beyond baseline.

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 clearly states the tool's function: saving the HTML cover of the page, and specifies it's the first thing visitors see. It distinguishes this from other page-related tools by focusing on the cover specifically. The verb 'Save' plus resource 'HTML COVER' is explicit.

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?

While it doesn't name alternative tools, it gives clear context on when to use this tool (to set the cover) and includes usage details like empty html clearing to default and auth requirements. The purpose is so specific that an agent would know when to invoke it, but it lacks explicit 'when not to use' or alternative routing.

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