Runs a new execution thread.

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

Annotations already declare this is a non-read-only, non-idempotent, non-destructive, closed-world write, so the safety profile is covered. The description usefully adds lifecycle context (threads can be continued or stopped), but omits what happens on repeated invocation and, importantly, never says a thread identifier is produced for later use.

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 short sentences, front-loaded with the action and followed by lifecycle context; nothing is padded. The middle sentence is slightly garbled ('used to start, work with a browser instance'), a minor polish issue rather than bloat.

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-optional-parameter tool with no output schema, the description covers purpose and lifecycle adequately. However, because no output schema exists, the description carries the burden of telling the caller that a thread handle is returned for continue/stop, and it does not.

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% and the only parameter's semantics (workspaceId, -1 = default) are fully documented in the schema. The description's phrase 'in the specified workspace' adds nothing beyond the schema and documents no format or constraint details, so the baseline 3 applies.

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+resource ('runs a new execution thread in the specified workspace'), which separates it from continue_use_thread and stop_thread. It does not distinguish itself from bulk_create_thread or start_browser_instance, which are the closest siblings an agent could confuse it with.

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?

Explains the thread's role (start/work with a browser instance) and explicitly routes to continue_use_thread and stop_thread for the follow-up lifecycle steps. It stops short of saying when to prefer this over bulk_create_thread or why a thread is needed instead of start_browser_instance directly.

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