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

Adds substantial context beyond the annotations: one-reminder-per-user-per-task upsert behavior, role restriction excluding Guests, and the fact that rescheduling re-arms the email even after it has fired. These are non-obvious behavioral traits an agent could not derive from readOnlyHint/idempotentHint 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?

Four sentences, each carrying a distinct piece of information: purpose/upsert, permissions, rescheduling effect, and the timezone contract. The purpose is front-loaded and nothing is padding.

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 two-parameter mutation with no output schema, the description covers what it does, who may do it, what it overwrites, and the single biggest correctness trap (UTC vs local time). Nothing an agent needs in order to call it correctly is missing.

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 both parameters are already documented, but the description adds real meaning: remindAt must be an absolute UTC instant, and it contrasts this with task start/end dates that are local wall-time, instructing the agent to convert before calling. Minor duplication of the ISO-8601 example keeps it from a 5.

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 ('Create or reschedule the caller's reminder on a task') and immediately clarifies the upsert semantics ('one reminder per user per task — this upserts'). An agent can distinguish this from delete_task_reminder and list_my_reminders without opening a 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 eligibility context ('Any team role (not Guest) may set their own reminder') and explains that rescheduling re-arms an already-fired email, which tells the agent when reusing the tool is appropriate. It does not explicitly point at delete_task_reminder or list_my_reminders as alternatives, so it stops short of full routing guidance.

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