pix_get_thread_timeline

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

Beyond the annotations (readOnly, idempotent, non-destructive), the description discloses important behaviors: each row is one PIXBeginEvent/End pair with name, span, and nesting depth; omitting stack_level flattens the tree; and duration vs execution_time captures time spent descheduled. It also defines the empty-result case. This is rich, non-obvious behavioral detail that an agent would not get from the schema or annotations.

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 well-structured: a one-line purpose, then a concise explanation of row semantics and the key stack_level/timing behaviors, then an actionable empty-case note. Every sentence adds value, and there is no repetition of schema or annotation content.

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?

With an output schema present, the description does not need to list return fields, and it covers the most important semantic nuances: flattening, timing interpretation, and empty results. The main gap is that several optional filtering/pagination parameters are left to name-based inference, but the tool is still usable by an agent given the clear overall framing.

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 0%, so the description must compensate for explaining the 8 parameters. It does explain stack_level behavior meaningfully and touches on duration/execution_time output semantics. However, it does not describe start_time, end_time, limit, cursor_position, timeout_seconds, or the required capture_id/thread_id beyond what their names imply. The compensation is only partial for a tool with this many parameters.

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 opens with a specific resource and intent: 'One thread's named PIX scopes: what it was doing, and for how long.' This is more than a restatement of the tool name; it identifies the exact scope of the tool and distinguishes it from broader GPU or event-level tools. The framing as 'the lane PIX draws for a thread' reinforces the unique positioning.

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?

The description conveys a clear usage context: use this when you need a single thread's PIXBeginEvent/End scope timeline with nesting and timing information. It also provides a specific fallback for empty results ('Check pix_get_timing_summary'), which is actionable. It does not systematically contrast with all sibling tools, but the resource and output semantics make the primary usage clear.

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