chrome_focus

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

With no annotations, the description carries the full burden. 'Fails closed instead of guessing or clicking' is a genuinely useful disclosure that there is no implicit fallback and no synthetic click, but it says nothing about the visible effect of focusing (keyboard focus movement), permission requirements, or the failure signal returned.

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, front-loaded with the action and target, with the failure policy second. 'Guessing or clicking' is slightly redundant with 'fails closed', keeping it just under maximum efficiency.

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 two-required-parameter, fully documented schema with no output schema, the description supplies what the structured fields don't: the prior-call dependency and the fail-closed policy. Only the observable effect of a successful focus is left implicit.

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%, so both node_id and snapshot_id are already documented in the schema. The description restates the snapshot lineage ('immediately preceding chrome_read') and the node constraint ('focus-capable') but adds no format or syntax detail beyond the schema, so 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 (focus) and resource (one exact focus-capable node) and scopes it to a node from the immediately preceding chrome_read snapshot, which separates it from the AX-family sibling ax_focus. It does not name an alternative explicitly, but the chrome_read lineage plus the 'focus-capable' qualifier make the target 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?

Gives a concrete precondition: the node must come from the immediately preceding chrome_read snapshot, implying chrome_read is a required prior call. No exclusions or named alternatives (e.g. when to prefer ax_focus) are provided, so it stops short of a 5.

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