session_start

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

With no annotations, the description carries the burden and it does disclose the key behavior: state (scroll, input, clicks) persists between commands and the session lives in a persistent tab until session_end. It does not detail error handling, auth, or resource costs, but it captures the critical stateful trait needed for correct 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?

Information is front-loaded and organized with WHEN/NOT WHEN markers. The repeated 'like a human in one tab' phrase is slightly redundant, but the listing of related session_* commands is useful and the overall length is reasonable.

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 stateful browser tool with no annotations, the description covers lifecycle (start, operate, inspect, close), routing, and state persistence. It omits max_chars semantics and behavior on repeated starts, but an output schema exists and the main interaction flow is clear.

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 coverage is 0%, so the description must compensate. It references the URL concept but never names the url parameter or explains requirements/defaults. max_chars is entirely absent, leaving one of the two parameters semantically unexplained.

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 opens with a specific action ('starts a live session') and names the exact resource (persistent tab of serve-worker). It clearly contrasts with fetch_page and browser_click, so an agent can distinguish session_start from its siblings without inspecting schemas.

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 WHEN/NOT WHEN section: use for interactive stateful operations; use fetch_page for text-only needs and browser_click for one-time URL click. It also lists the follow-up session_* commands and how to close, giving complete routing guidance.

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