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

readOnlyHint=true already establishes this as a safe, non-mutating read, so the bar is lower. The description still adds real context beyond the annotation by characterizing the payload — full trace, all spans, timings, nesting — plus the underlying endpoint (GET /api/v1/runs/{runId}/trace). It does not mention payload size or pagination/truncation behavior for large traces, which is the remaining gap.

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?

Three tight clauses: what it returns, when to reach for it, and the backing endpoint. The return scope is front-loaded and nothing is padded or repeated.

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 no output schema, the description carries the return-value burden and does reasonably well by naming spans, timings and nesting level. Given annotations cover the safety profile and there is only one simple parameter, the definition is nearly complete; only payload-size/pagination caveats are missing.

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?

Only one parameter, and schema description coverage is 100%, so the schema fully documents run_id. The description adds no format hints (e.g. where to obtain a run id) beyond what the schema provides; 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 (fetch), resource (a run's execution trace) and scope ('every span, with timings and nesting'), which clearly distinguishes it from sibling trigger_get_run_span and trigger_get_run. An agent can tell what it gets back without opening any schema.

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 framing "where did this run spend its time, and where did it break?" gives an explicit diagnostic use case, which is strong practical guidance. It stops short of naming alternatives (e.g. get_run_span for a single span) or stating exclusions, so it is clear context rather than full when/when-not routing.

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