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

ReadOnlyHint and openWorldHint already signal that this is a safe, externally-bound read operation. The description adds meaningful behavioral context beyond annotations: it executes JavaScript, waits for rendering, and returns the final DOM as HTML text. This helps the agent understand that it is a browser-like operation, not a simple HTTP fetch.

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 tight sentences with no filler. It front-loads the core purpose, immediately gives practical usage guidance, and closes with the output format. Every sentence serves a distinct, useful purpose.

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 fetch tool with a fully documented parameter schema, the description covers the essential context: what the tool does, when to use it, and what it returns. With readOnlyHint and openWorldHint present, plus rich schema descriptions for all parameters, nothing critical is missing for an agent to select and invoke this tool correctly.

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 the parameters (url, wait_for, max_chars) are fully documented in the schema. The description does not add extra parameter-level detail, but it does provide useful context in the form of 'after JavaScript has executed' that implies why wait_for might be relevant. This meets the baseline for schema-heavy coverage.

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 uses a specific verb ('Fetch') and a clear resource ('a page's HTML after JavaScript has executed'), and distinguishes this from a plain HTTP fetch. It also states the output ('final DOM as HTML text'), making the tool's purpose unmistakable and distinct from sibling tools like screenshot_url or inspect_element.

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 explicitly says when to use this tool: when a plain HTTP fetch returns an empty shell or loading spinner, such as with SPAs or client-side rendered sites. It clearly identifies the alternative scenario, though it does not explicitly name sibling tools or state when not to use this tool in favor of them.

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