session_info

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

With no annotations, the description carries the burden of disclosing behavior. It reveals that the session might be attached to different devices ('real iPhone' vs 'Mac Safari') and frames the tool as a verification step, implying read-only behavior via the verb 'report.' It adds useful context about session state.

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 sentences: the first states the primary action, the second gives usage guidance. It is front-loaded, direct, and contains no redundant information.

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 the tool's simplicity (0 parameters, no output schema, no annotations), the description covers purpose and usage scenario adequately. It does not detail the exact return format, but for a session-info tool, 'report what device/browser' is sufficiently clear for the agent to understand what to expect.

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?

The tool has zero parameters, which sets a baseline of 4. There is no need to describe parameter semantics beyond what the empty schema already conveys, and the description appropriately focuses on the tool's purpose.

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 clearly states the tool's function: 'Report what device/browser this session is actually attached to.' It uses a specific verb ('report') and resource ('device/browser'), and distinguishes itself from sibling action-oriented tools like navigate, click, and screenshot.

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 provides explicit when-to-use guidance: 'Use this first to confirm you are driving the real iPhone and not Mac Safari.' It identifies a concrete scenario and priority, but does not explicitly state when not to use the tool or name alternative tools.

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