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

Beyond the annotations (readOnlyHint=false, etc.), the description discloses rich behavioral details: the POST mechanism, 3 delivery attempts with backoff, the returned id doubling as a capability for inspection/cancellation, payload size limits, delay bounds, and the prerequisite of a verified origin. This fully informs the agent about side effects and required context.

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 description is concise yet comprehensive. Four dense sentences cover purpose, use case, prerequisite, limits, attempts, and return value without redundancy. It is front-loaded with the core function and each sentence adds meaningful information.

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?

Given there is no output schema, the description compensates by explaining what the caller receives (an id with inspect/cancel capability). It also covers the prerequisite dependency, time and payload constraints, and delivery behavior. This makes the tool's complete contract clear to the agent.

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. The description enhances parameter understanding by explaining that the payload is 'JSON string delivered as the request body', tying url verification to the prerequisite, and noting that the returned id is for subsequent control. These additions go beyond the schema's per-property descriptions.

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 opens with a precise, action-oriented statement: 'Schedule a durable callback: at fire time this service POSTs your JSON payload to your URL.' This clearly identifies the tool's function and differentiates it from sibling tools like timer_cancel and timer_status, which manage or inspect existing timers.

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?

The description gives explicit guidance on when to use the tool: 'Use it to wake up future runs of yourself or your orchestrator - agents cannot wake themselves.' It also states a critical prerequisite involving timer_verify_origin. It doesn't explicitly mention alternatives or when-not-to-use, but the use case is clear enough to distinguish it from immediate request tools.

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