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

Annotations declare readOnlyHint=false, idempotentHint=false and openWorldHint=true, so the agent already knows this mutates external state and isn't repeatable. The description adds domain-specific behavior the annotations cannot convey: that it moves the session's history pointer and that the underlying action differs between browser and mobile sessions. It does not say what happens when there is no history to go back to, which is the main remaining gap.

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 sentences, front-loaded with the core action before the routing detail. Dense but every clause (platform semantics, addressing key, alternatives) carries information; the sibling list is long but justified given the many near-duplicate back/navigation tools.

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?

With no output schema, the description should ideally indicate what a successful back returns (e.g., the new current URL/page), and it does not. Otherwise it is complete for a one-parameter navigation tool: action, scope, addressing, and alternatives are all covered.

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?

One parameter with 100% schema description coverage, so the schema already documents sessionId as 'Session ID'. The description adds only that the tool is 'addressed by sessionId', which is a baseline restatement rather than new syntax or format meaning.

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 effect ('Go back one entry in the history of a WebDriver session') and disambiguates the semantics per platform: browser Back vs. the mobile platform back action. An agent can tell exactly what this does and how it differs from sibling navigation tools without opening a 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?

Explicitly names the alternatives and the condition that selects each: no forward counterpart here, use web_back/web_forward by pageId on a desktop grid page, webpage_back or device_key by udid on a real device. This is direct routing guidance, not implied usage.

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