start_profiling

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

Annotations only declare the mutation/idempotency profile; the description adds the operationally important facts an agent can't get from them: profiling keeps running until stop_profiling, calling again fails while a recording is active and the existing one continues, and higher sampling costs overhead and a larger profile. It also mentions the return value (a confirmation).

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?

Front-loaded with the action and default, then workflow, then tuning, then failure mode. Dense but nearly every clause carries information; the sampling discussion is the one place it could be trimmed slightly.

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 stateful, non-idempotent tool with no output schema, the description covers the full lifecycle (start → reproduce → stop), the failure mode, and the fact that it returns a confirmation. An agent has everything needed to call it correctly and clean up.

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; the description still adds real meaning by explaining when to deviate from the 1000µs default and what the tradeoff is, plus that tabIndex defaults to the active tab. It adds rationale rather than restating types, though it doesn't tie advice to each parameter individually.

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 ('Start the V8 CPU profiler on a tab') with scope clarified (active tab by default, or tabIndex). Immediately distinguishes itself from list_network_requests by naming the excluded concern (network slowness) and points at stop_profiling as its pair.

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 an explicit workflow (start, reproduce, then stop_profiling on the same tab), an explicit when-not (network slowness → list_network_requests), and concrete tuning advice for samplingIntervalUs. Alternatives and exclusions are both named rather than inferred.

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