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

Annotations already declare readOnlyHint=true, so the safe-read profile is covered structurally. The description adds that the span comes with its own logs and attributes, which is useful return-shape context, but says nothing about auth, pagination, or tracing behavior.

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?

Two tight sentences with the resource description front-loaded and the REST path appended. No filler, though the endpoint line adds little for an agent that already knows the parameters.

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 two-parameter read tool with full schema coverage and a readOnlyHint, this is nearly complete; it even hints at the returned payload. The one gap is the missing disambiguation from trigger_get_run_trace.

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% and both required parameters are documented in the schema itself, so the description isn't needed to explain them. It adds only the endpoint template showing runId/spanId placement, which is marginal beyond the schema.

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 ('Fetch a single span from a run's trace'), which sets it apart from most siblings. It doesn't explicitly distinguish itself from the closest sibling, trigger_get_run_trace (whole trace vs one span), so an agent must infer that boundary.

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?

No when-to-use guidance, no prerequisites, and no alternatives named. The obvious alternative, trigger_get_run_trace, is never mentioned even though the two overlap heavily in intent.

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