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

Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=false, but the description adds meaningfully more: partial-update behavior, and the non-obvious runtime semantics of pausing (pings still recorded, nothing judged or alerted, an open outage closes without a back alert) and resuming (waits for the next ping). These are behavioral traits an agent could not infer from the structured fields and are exactly what prevents misuse of the paused flag.

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 front-loaded sentences ordered by importance: what can change, how partial updates behave, then the pause/resume semantics. The parenthetical about outages and back alerts is dense but earns its place by describing a surprising behavior. Slightly long for the operation, but no sentence is 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?

With all 7 parameters documented in the schema, no output schema, and annotations covering the safety/idempotency profile, the description supplies exactly the missing pieces: partial-update semantics and pause/resume runtime behavior. An agent has everything needed to call this correctly, and return values need not be described without an output schema.

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, and the description lifts it by explaining the cross-parameter interaction implied by the pause/resume and partial-update model. It does not restate the schema's ranges or the cron/period switch mechanics, but the schema already documents those thoroughly.

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 verb and resource ('Rename a heartbeat, change its period or grace, or pause / resume it') and enumerates exactly which fields are mutable, so an agent immediately knows the operation's scope. It also clarifies that deletion is out of scope ('Deleting a heartbeat stays in the dashboard'). It stops short of naming the nearest siblings (list_heartbeats, add_heartbeat, pause_monitor_group) so it falls just short of explicit sibling differentiation.

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 gives clear context for use: partial-update semantics ('Only the fields you pass change') and the conditions under which pausing versus resuming is appropriate, including the consequence of each state. It also excludes a neighboring action (deletion is done in the dashboard), which routes the agent away from a non-existent capability. No sibling tool is named as an alternative, so it lacks explicit when-not guidance.

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