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

Annotations already declare the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false), so the agent knows this mutates navigation state non-idempotently. The description adds the desktop-scope constraint, but says nothing about what happens at the start of history (no prior entry) or what the call returns. That is a modest addition on top of structured data.

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 short sentences, zero waste, with the operation and its scope front-loaded and the routing caveat immediately after. Nothing could be removed without losing 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?

For a single-parameter navigation tool with no output schema and no nested objects, the description covers what an agent needs to select and call it, including the sibling disambiguation. It stops short of describing failure behavior when there is no history entry to go back to.

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 at 100% schema coverage, where the schema itself documents pageId as 'Page ID from web_navigate'. The description only echoes 'by pageId' and adds no format, origin, or constraint detail beyond the schema, so the baseline 3 applies.

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 ('go back one history entry in the DESKTOP grid browser') and immediately scopes it against the device sibling webpage_back. An agent can distinguish web_back from webpage_back 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?

Explicit routing guidance in both directions: use this for the desktop grid browser, and 'Not a device — for a phone or tablet use webpage_back.' The when-to-use and the alternative are both named.

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