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

Beyond the annotations it adds real behavioral context: owner-only gating on approve_plan, approve and autonomy, the phase-based validity of each event, and that all problems in an event are returned together with their field path. It does not explain what a rejected/out-of-order event does to the engagement, but it goes beyond what readOnly/idempotent hints convey.

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 core action is front-loaded and the phase rules are compressed into two tight sentences with no filler. The telegraphic, semicolon-joined style is dense but readable; a slightly clearer separation of the phase lists would cost nothing.

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 three-parameter but deeply polymorphic schema with an output schema present, the description covers the event taxonomy and phase legality, which is the main thing an agent must get right. It leaves payload-level requirements to the schema, which is appropriate, and omits only error/rollback behavior.

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 the schema already documents engagement, engagement_sha256 and the oneOf event union in detail, so the baseline applies. The description mostly restates the event-type list rather than adding field-level meaning for the nested brief/plan payloads.

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 first sentence gives a concrete verb+resource: 'Apply one event to an engagement', and the rest enumerates the event vocabulary (brief, plan, approve_plan, data, start, complete, approve, skip, block, reopen, next_round). It never names a sibling, so the boundary with start_outcome (which clearly also covers engagement initiation) and record_outcome_decision is left for the agent to infer.

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?

It specifies which events belong to which phase ('Before the run: brief ... plan ... approve_plan', 'During the run: ...'), notes that a plan event mid-run is a revision, and that autonomy is valid any time. That is genuine when-to-use routing per event type, though it says nothing about when not to call this tool or which sibling to use instead.

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