session_create

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

With no annotations, the description carries the full behavioral burden. It does disclose that the tool launches the engine, creates a fresh coherent identity, and returns a session_id, which is useful. However, it omits session lifecycle details, cleanup expectations, resource cost, or side effects of reusing a profile_dir.

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 two short sentences, front-loaded with the action, and each sentence contributes: one defines what the tool does, the other states the essential output. There is no filler or repetition.

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 session-creation tool with no output schema and no annotations, mentioning session_id is valuable. Still, the description lacks lifecycle context, usage ordering relative to other tools, and any error or cleanup behavior, making it minimally complete rather than fully actionable.

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 input schema already explains proxy, headful, platform, and profile_dir with helpful detail. The description adds no parameter-level meaning, but the schema carries that burden fully, 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?

The description uses a specific verb and resource ('Create a new browsing session'), states the engine-launching behavior, and notes the key return value (session_id). It also distinguishes itself from siblings like page_open and identity_generate by framing this as the session-level creation step.

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 such as identity_generate or page_open, and no prerequisites or ordering constraints are mentioned. An agent must infer that creating a session should precede page operations.

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