create_reminder

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

Annotations already establish readOnlyHint=false and destructiveHint=false, so safety is covered. The description adds real behavioral context beyond that: the reminder persists and syncs to the iPhone, and omitting due/list_name yields a timeless reminder in the default list. It omits what the call returns, but no output schema exists and the mutation semantics are otherwise clear.

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-loads the one-line purpose and sibling contrast, then a compact args block where every line earns its place given zero schema coverage. No filler or restated boilerplate.

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 3-parameter mutation tool with annotations and no output schema, the description covers purpose, differentiation, and every parameter's semantics. The only gap is the absence of any statement about the return value or duplicate-handling, which is minor for a create operation.

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 carries the full burden and does so: it explains title, gives the exact due format '2026-09-14 20:00' plus the meaning of omission, and explains that omitted list_name falls back to the default list. This is meaning the schema alone does not convey.

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 ('Add a reminder in the Reminders app') and immediately distinguishes it from the sibling tool notify by contrasting ephemeral notifications with a persistent, syncing reminder. An agent can tell this apart from list_reminders and notify without opening any schema.

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?

Gives clear selection context by contrasting with notifications ('Unlike a notification, this persists and syncs to the iPhone'), which tells the agent when to prefer this tool over notify. It does not, however, reference list_reminders or state any prerequisites, so it stops short of 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.