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

Annotations already declare readOnly=true, idempotent=true, destructive=false and closed-world, so the safety profile is covered. The description goes beyond that by disclosing that event payloads are third-party input labelled untrusted and by explaining the paging contract via `next_since`. That is genuinely useful context not present in the annotations or schema.

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 dense sentences, zero filler, with the scoping rule (sequence order after `since`) front-loaded, followed by content enumeration, the untrusted-data warning, and the paging hint. Every sentence carries load.

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?

There is no output schema, so the description must carry the return-value burden, and it largely does: it describes what each event contains, its ordering, and the `next_since` cursor. The untrusted-data label covers a security concern an agent needs. Only the `limit` parameter and the exact response shape remain unaddressed.

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 only 33% (`since` is documented, run_id and limit are not), so the description is expected to compensate. It clarifies `since` semantics and introduces `next_since` for paging, but says nothing about `limit` (max 200) or the run_id requirement. Partial compensation only, so baseline 3.

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 names a specific resource (the run's timeline of events) and scopes it (sequence order after `since`), then enumerates the concrete content types: mail, callbacks, mock calls, forwarding results, faults. An agent immediately knows this is a read of recorded events. It stops short of naming how it differs from siblings like rig.event.wait or rig.event.replay, so sibling differentiation is left to inference.

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?

Usage guidance is implied rather than explicit: it tells you to page with `next_since` and that ordering is by sequence after `since`, which is enough to call it. But it never states when to prefer this over rig.event.wait (live waiting) or rig.event.replay (re-execution), which are the closest alternatives. Adequate but with a clear routing gap.

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