Open Firefox View

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

readOnlyHint=false is consistent with a tool that creates a tab, and the description corroborates that a new tab is opened via bBrowser.addTab with no privileged API needed. However, the implementation note is developer-facing trivia rather than agent-relevant behavior: it does not say whether the new tab becomes active, whether an existing Firefox View tab is reused, or what the call returns. The safety profile is adequately covered by the annotation, so a 3 is appropriate.

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 opening sentence is well front-loaded and the closing routing sentence earns its place. The middle 'MEASURED: it is a plain about: page, so no privileged API is needed — bBrowser.addTab suffices' is internal implementation justification that an agent cannot act on and dilutes an otherwise two-sentence definition.

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 one-optional-parameter, no-output-schema navigation tool, the description covers what opens and how it differs from the nearest sibling. Only minor gaps remain (foreground vs. background default, whether an existing view tab is focused), which are low-cost for an agent to discover by calling it.

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?

Only one optional parameter (background) and the schema already documents it at 100% coverage ('Open in the background'). The description never references the parameter, so it adds nothing beyond the schema; baseline 3 applies when the schema carries the full burden.

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 (open) and a specific resource (the about:firefoxview page), then enumerates what that page shows (recently closed tabs, tabs from other devices, sync status). It also explicitly names the sibling it is not — browser_open_about_page — so an agent can pick between them without opening a schema.

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 third sentence gives a clear routing rule: firefoxview is a browser/ page rather than a toolkit page, which is why it lives in its own tool instead of browser_open_about_page. That is genuine sibling-level guidance, though it is framed as an explanation of design rather than an explicit 'use this when / not when' instruction, and it says nothing about prerequisites or side effects.

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