open_tab

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

With no annotations provided, the description carries the full burden and exceeds it: it discloses side effects (creates tab, registers Tab ID, stays open until closed), lazy instance launch, and the exact return structure (tab_id, target_id, url, label). This level of detail would be expected even if annotations existed.

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 compact—four sentences covering action, side effects, prerequisites, return, and alternatives—with the core purpose front-loaded. Every sentence adds value, and there is no filler.

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 tool with 3 optional parameters, no output schema, and no annotations, the description covers all essential aspects: what it does, side effects, prereqs, return value, and how its output fits into the tool ecosystem. An agent has everything needed to call it correctly.

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 baseline is 3, but the description adds meaningful context for each parameter: 'url' defaults to about:blank, 'label' has a uniqueness constraint, and 'instance_id' is tied to open_instance/list_instances. It also explains that the returned tab_id is used as argument elsewhere, enriching parameter semantics beyond the schema.

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 states a specific verb ('opens'), resource ('new tab in the specified Chrome instance'), and clearly distinguishes it from siblings by naming alternatives like 'navigate' and 'list_tabs'. It also explains its purpose for parallel work with isolated CDP state, leaving no ambiguity about what the tool does.

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 provides when to use ('Use this to work with several pages in parallel while keeping their CDP state isolated per tab') and names two direct alternatives ('navigate' for active tab, 'list_tabs' for enumeration), enabling an agent to select the correct tool with no inference needed.

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