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

Annotations already declare this is a non-read, non-destructive mutation, and the description adds the behavior that matters: the effect is to suppress re-notification, it is scoped to the current user and, in an agent run, to the run's agent. It does not say whether the call is idempotent or what happens to IDs outside that scope, so it stops at 4.

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 short sentences, front-loaded with the action, then the usage trigger, then the scoping caveat. No restatement of the title and no filler.

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 mutation with no output schema and annotations covering the safety profile, the description covers action, timing, and scope adequately. It leaves open the return value and partial-failure behavior, which is a minor rather than blocking gap.

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 the baseline is 3, but the description adds a real constraint on which event_ids are valid — only events belonging to the current user or the run's agent are affected. That is scope information the schema does not express.

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 (mark monitor events) plus the exact state transition applied (as included in a digest notification). An agent can tell immediately this is the write-side counterpart to search_monitor_events rather than a search or listing tool.

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?

"Call this after composing a Slack digest to prevent re-notifying the same events" gives a concrete trigger condition and ordering, which is exactly the guidance needed for a bookkeeping mutation. It stops short of naming when not to call it or pointing at search_monitor_events as the discovery step, so it is short of a 5.

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