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

Goes beyond the annotations by disclosing real side effects: a push notification and an email are dispatched, and relative reminders track the due date and repeat with repeating tasks. This is meaningful behavior an agent could not infer from readOnlyHint=false / destructiveHint=true / openWorldHint=false alone.

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?

Front-loaded with the action and its effects, then the scheduling semantics, with no filler sentences. The second clause is dense and slightly run-on, but every element carries information the agent needs.

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 5-parameter mutation tool with no output schema, the description covers effects and both scheduling modes well, and the annotations carry the safety profile. It could still note the required `cardId` explicitly and mention whether the reminder is immediately active or error 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 0%, so the description must carry the burden, and it does: `at` is defined as an ISO 8601 instant, `timeZone` as IANA, and `daysBefore` + `time` as a due-date-relative offset. Only `cardId` is left implicit via the phrase 'on a task', which is a minor gap.

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 ('Adds a reminder for the user on a task') plus the concrete effect (push notification and email), which cleanly separates it from list_reminders and remove_reminder among the siblings.

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 effectively explains the two mutually exclusive ways to schedule the reminder ('Either `at` ... or relative to the due date'), which tells the agent which parameter set to choose. It stops short of stating when to prefer this tool over list_reminders/remove_reminder or any prerequisite conditions.

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