Creates a new browser instance for the specified profile.

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

Annotations already declare readOnlyHint=false, idempotentHint=false, and destructiveHint=false, so the write/non-idempotent profile is known. The description adds nothing beyond that: it never says a browser process is launched, what happens if the profile is already running, whether the instance persists after the call, or which permissions/limits apply. For a process-spawning tool this is thin.

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?

One sentence, no filler, and the core action is front-loaded. It is slightly redundant in restating 'the new browser instance' from the title, but nothing is bloated.

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 7-parameter, non-idempotent creation tool with no output schema and no annotations covering side effects, the description should say what the call produces (an instance handle/id?) and what can go wrong. None of that is present, so an agent cannot anticipate the result or failure modes.

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 each of the 7 parameters is already documented, including defaults for threadToken and workspaceId. The description only loosely gestures at 'profile, workspace and desktop settings' and adds no syntax or interaction detail (e.g., how customFeatures overrides environmentTags). 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?

The description states a specific verb and resource ('creates the new browser instance using the specified profile'), so an agent knows this spins up a browser tied to a profile. It does not, however, distinguish itself from the sibling bulk_start_browser_instance or explain the singular-vs-bulk split. Clear purpose, but no sibling differentiation.

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?

There is no guidance on when to use this rather than bulk_start_browser_instance, nor any stated prerequisites (profile must exist, whether the profile can be locked/in use, whether a thread or proxy is needed). The optional parameters are mentioned but never framed as usage conditions.

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