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

Annotations only include a title, so the description carries the full burden. It discloses that the source session stays untouched (non-destructive) and that the new session carries the full login state. This is adequate for a clone operation, though it does not mention any potential side effects such as resource usage or failure modes.

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?

Three sentences, each earning its place: the first states purpose and contents, the second adds the key safety note, and the third provides usage and return format. Purpose is front-loaded, and there is no fluff.

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 a single parameter, no output schema, and no annotations, the description covers purpose, behavior, usage scenarios, and return format. An agent has everything needed to decide when and how to call it correctly.

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 100% for the single parameter, with a clear description ('Session ID to derive from (stays alive and untouched)'). The tool description reiterates that the source is untouched but adds no new meaning beyond the schema. Baseline 3 is appropriate.

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 states a specific verb 'derive' and resource 'browser session', enumerates what is carried (cookies, localStorage/sessionStorage, viewport, etc.), and explicitly notes the source is untouched. This clearly distinguishes it from sibling tools like session_cookies or session_storage, which handle individual aspects.

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?

It gives explicit use cases: 'snapshot a logged-in state before risky actions' or 'run the same login in parallel tabs.' While it does not name alternatives or provide explicit when-not guidance, the context makes it obvious that this tool is for whole-session cloning, whereas siblings are for parts. Strong guidance overall.

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