Current toolbar layout

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

readOnlyHint already declares the safety profile, so the bar is lower. The description nonetheless adds real context: the data is sourced from browser.uiCustomization.state and the returned widget ids are exactly the format browser_set_toolbar_widget accepts, which prevents an id-mismatch failure during a restore.

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 tight sentences: scope first, source and id semantics second, workflow third. Nothing is repeated and 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 single-param read tool with annotations and no output schema, this covers scope, source, id compatibility and workflow. It stops just short of saying anything about the return shape (per-area arrays of ids), which would have made it fully self-sufficient.

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 and schema description coverage is 100%, so the schema already documents 'area' with an example and the default of every area. The description's mention of areas matches but does not extend the schema, so the baseline 3 is appropriate.

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 — 'List which widgets sit in each toolbar area' — and names the underlying source (browser.uiCustomization.state) plus concrete area examples (nav-bar, TabsToolbar, PersonalToolbar). It is clearly the read counterpart to browser_set_toolbar_widget, so an agent can separate it from siblings without opening the 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?

Explicit sequencing guidance: 'Read this before changing the layout, and use it to put things back afterwards.' This tells the agent both the pre-condition and the restore workflow, and implicitly points at the mutation sibling that motivated it.

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