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

With no annotations, the description carries the full burden, and it does disclose two real behavioral traits: the session is private/server-side and each call costs 1 mcp_call. It omits what happens on navigation failure, whether an existing session's state is preserved, and any timeout/auth behavior beyond the saved-login note.

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?

Two tight sentences, front-loaded with the core action, then the one non-obvious parameter behavior and the cost. No wasted words and no repetition of the schema.

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?

No output schema and no annotations mean the description is the only behavioral source, and for a 3-parameter tool with 0% schema coverage it leaves the 'session' parameter and failure/return behavior undocumented. What it does cover — session privacy, saved-login loading, cost — is the right kind of information, just incomplete.

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%, so the description must compensate. It explains browser_session_label well (loads a saved login on first session creation, with a pointer to browser_session_put), but says nothing about the 'session' parameter (default 'default') or whether url accepts any scheme — partial compensation only.

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 and resource ('Open a URL') plus the scope ('your private server-side browser session'), which clearly separates it from action siblings like browser_click or browser_extract_text. It never explicitly names those siblings as alternatives, so it falls short of a 5.

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?

Usage is implied rather than stated: the agent can infer this is the entry point before browser_click/browser_fill, and the description does say when browser_session_label matters (first session creation) and points to browser_session_put. It gives no explicit when-to-use vs. when-not, and no guidance on navigating again within an existing session.

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