get_performance_metrics

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

With no annotations provided, the description discloses key behavioral traits: it explicitly notes 'Side effects: none (read-only snapshot)' and 'Prerequisites: requires an active Chrome tab'. It also specifies the return format. This is strong coverage, though it doesn't mention what happens if no active tab exists or whether there are rate limits, which are minor gaps.

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 structured logically: purpose, side effects, prerequisites, returns, usage, alternatives. Each sentence adds value and information is front-loaded. It is slightly longer than necessary but remains efficient and scannable.

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 tool's simplicity (2 optional parameters, read-only, returns JSON), the description is fully complete: it explains the return structure with examples, includes side-effects and prerequisites, and gives usage guidance. An agent can call this tool correctly without any further information.

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 description coverage is 100%, so the schema already fully documents both parameters (tab_id and instance_id). The description adds no additional nuance beyond the schema's existing explanations. With full schema coverage, the baseline of 3 is appropriate; the description does not need to compensate much.

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 tool captures runtime performance metrics (JS heap size, DOM node count, layout timing) and explicitly distinguishes it from 'profile_page_performance' which does detailed tracing. It identifies both the verb and resource precisely, making it unambiguous among siblings.

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 explicitly states when to use the tool ('monitor memory usage, detect memory leaks, or profile performance') and names the alternative ('profile_page_performance' for detailed tracing, plus browser DevTools Performance tab). This provides a clear decision pathway without needing to inspect other tool definitions.

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