browser.start_session

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

The phrase 'Creates or returns' discloses an important behavioral trait: the tool is idempotent and will return an existing session if one is already active. With no annotations provided, this is helpful, but the description omits other behavioral details such as side effects, required setup, or state resets, leaving the agent underinformed.

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 description is a single concise sentence with no wasted words, but it is under-specified. While it earns its place by stating the core operation, it lacks critical details that a slightly longer description could have provided, making it concise yet incomplete.

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?

Given the tool's role as a session initializer with 3 parameters, no output schema, and no annotations, the description is severely lacking. It does not explain the return value, prerequisites, or how this fits into the workflow of the sibling tools. The agent would not know when or why to call this tool.

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 0%, meaning the description must compensate for the lack of parameter documentation. The description mentions none of the parameters (locale, headless, timezone) and provides no guidance on their meaning or usage. The schema only lists names and defaults, which is insufficient.

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 clearly states the tool's action ('Creates or returns') and resource ('controlled browser session'), making it obvious this is a session management tool. However, it does not differentiate itself from siblings like browser.open_url or browser.inspect_page, nor does it explain what 'controlled' means in this context.

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 description gives no guidance on when to use this tool versus alternatives. It does not mention that this should be called before other browser tools, nor does it describe any prerequisites or exclusions. No context signals are provided in the description.

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