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

Goes well beyond the annotations (readOnlyHint=false, idempotentHint=true, destructiveHint=false) with three non-obvious behavioral facts: it runs in the recorded browser's own profile, the browser stays signed in afterward, and the agent never sees the user's keystrokes. The privacy and persistence details are exactly what an agent needs before invoking an interactive login.

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?

Front-loads purpose, then the procedural steps and privacy note, then a terse parameter glossary. The second sentence is load-bearing despite being procedural. The trailing parameter fragment is appended rather than integrated, a minor structural blemish.

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 an interactive flow with no output schema and 4 undocumented params, the description covers the essential behavior: what the agent must tell the user, that credentials are never exposed, and that the session persists. What it returns and how the caller confirms completion are left implicit, but annotations cover the safety profile.

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 carry the burden. It lists response_detail (summary|compact|full), fields (dotted paths), and cursor (next page), which does supply semantics the schema lacks and adds enum values the schema omits. However, it defers to 'the server instructions' and says nothing about the required url parameter.

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 window on the user's screen... for the USER to sign in to a site') and names the sibling flow it hands off to (screen_open). An agent can distinguish it from screen_open without opening either schema.

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?

Provides an explicit workflow: open the window, tell the user to sign in and close it, then screen_open the page again. This gives clear when-to-use routing to the sibling. It stops short of stating when-not-to-use or edge cases, but the sequencing is unambiguous.

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