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

Annotations already declare this as a safe read operation (readOnlyHint=true, destructiveHint=false), so the bar is lower. The description adds genuine non-obvious behavior: each trace may map to multiple runs because of multi-agent execution, which the agent cannot infer 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?

Three tight sentences, front-loaded with the primary definition of the operation, followed by the use case and the multi-agent caveat. No filler and nothing repeated from structured fields.

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 burden of explaining the return shape, and it does so by enumerating ancestors/self/children and flagging the multi-run mapping. That is adequate for a two-parameter read tool, though it omits ordering or pagination details for the lineage.

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 both traceId and customerId are already documented in the schema, including the superadmin-only constraint on customerId. The description adds no syntax or format detail beyond the schema, so the baseline of 3 is appropriate.

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 (get) and resource (runtime trace lineage) and immediately defines what lineage means: ancestors, the trace itself, and children. This is clearly distinguishable from siblings like get_run or get_run_finding_context.

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 use case ('navigate multi-trace workflows, for example a design run that spawned an interview run'), which tells the agent when this tool applies. It stops short of naming an alternative tool or stating when NOT to use it, so it falls below the 5 bar.

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