Open a page in Reader View

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

Adds genuinely useful behavior context not present in annotations: the exact module path that works (moz-src:///...) versus the one that fails, and the about:reader?url=<encoded> URL convention. This is a real implementation gotcha an agent would otherwise stumble on. It doesn't cover permissions or what happens to the existing tab, and readOnlyHint=false is consistent with opening a tab.

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 compact sentences with the core capability front-loaded. The 'MEASURED' aside is technical but earns its place as an actionable implementation detail; nothing is padding.

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 two-parameter tool with no output schema, the description covers purpose and the tricky implementation path well. The one gap is that it doesn't say what is-readable returns (a boolean, presumably), which matters slightly since there is no output schema.

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% and both parameters are already documented, including the action enum. The description's about:reader detail adds marginal meaning to 'open' but nothing new about the 'context' parameter or token format.

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 and resource ('Open a tab in Reader View') plus a second mode ('report whether the current page is reader-able'), which is unambiguous. It also clarifies the underlying page form (about:reader?url=<encoded>), distinguishing it implicitly from browser_open_about_page/browser_navigate, though no sibling is named.

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 two modes are described, but there is no explicit guidance on when to choose this over browser_navigate, browser_open_about_page, or browser_page_info, nor any prerequisite for the is-readable check. Usage is inferable from the action names rather than stated.

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