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

Annotations only say this mutates state and is open-world; the description goes far beyond by disclosing consent requirements, confirm semantics, the exact reminder cadence (24h and seven days, one-hour grace, two reminders max per episode), cost ('Free; no email, credit spending, automatic restart or synthetic heartbeat'), and edge cases like renewed opt-in on receiver change and in-flight alerts still arriving. No contradiction with destructiveHint=true, since the mutation is clearly disclosed.

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 action and its gating condition are front-loaded, and the sentence-per-fact style keeps the dense caveats (cadence, cost, disable, receiver change) scannable. The telegraphic phrasing is terse but each clause carries distinct information, so little is wasted.

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?

An output schema exists, so return values need not be described. Given that, the description covers everything an agent needs to call this safely: prerequisites, consent/confirm gating, side effects, timing, cost, and the disable path.

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 description coverage is 0%, so the description must carry the parameter burden. It clarifies confirm (required when enabling, not needed when disabling) and enabled (opt-in/opt-out), but says nothing about agent_id or api_key, and never explains that the webhook receiver is implicit rather than a parameter.

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 gives a specific verb and resource: opting into quiet-agent recovery reminders over the agent's existing HTTPS webhook, and it scopes the feature with 'Heartbeat mode only.' It is distinguishable from most siblings, though it never names the obvious read counterpart (read_agent_reengagement), leaving the read/write split to be inferred from the tool name.

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 states the conditions that gate use (heartbeat mode only, explicit owner consent, confirm=true) and the disable path ('Disable without confirm'). It also advises using a durable supervisor/owner receiver independent of the worker. It stops short of naming alternatives such as read_agent_reengagement or the liveness subscription tools.

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