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

With no annotations provided, the description carries the full burden. It discloses that it returns ids and negotiated capabilities and covers browser and mobile sessions. It implies a read-only operation without explicitly stating it, and does not mention potential limitations like pagination or staleness, but for a simple list tool this is adequate.

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 three concise sentences: the first states the core function and output, the second gives concrete use cases, and the third clarifies a key distinction from a sibling tool. Every sentence contributes value without redundancy.

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 simplicity (no params, no output schema), the description is sufficiently complete. It tells an agent exactly when to call it, what it returns, and what it is not. An agent can confidently decide to invoke it without additional context.

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?

There are zero parameters, so schema coverage is trivially 100%. Per the baseline for 0 params, a score of 4 is appropriate. The description adds no parameter info because none exist, which is fine.

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 verb 'list' and the resource 'WebDriver sessions' on the testing grid, and explicitly distinguishes itself from device_list. It also mentions coverage of both browser and mobile sessions, making the purpose unambiguous.

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 provides explicit when-to-use scenarios: recovering a lost sessionId or checking node occupancy before opening another session. It also gives an explicit alternative (device_list) and states what this tool is not for, leaving no ambiguity.

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