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

Annotations only flag mutation and non-idempotency; the description adds substantial behavior the annotations cannot convey: the shared daily creation allowance, the specific `entitlement_required` failure with no scheduling, the "scheduled is not delivered" distinction, and that existing reminders survive plan termination. These are exactly the side-effect and failure-mode facts an agent needs before calling.

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 purpose and recipient scope, then boundaries, then failure behavior. Seven short sentences with no filler, though the allowance, entitlement, and plan-expiry points could be merged into fewer clauses without loss.

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 mutating tool with no output schema, the description covers what an agent needs: authorization precondition, ambiguity handling, dedupe expectations, quota failure signal, and the confirmation contract. Nothing material about invoking 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 description coverage is 100%, so every parameter including the `request_id` retry key is already documented in structured data. The description reinforces the ambiguity-clarification expectation for text/time/timezone but adds no syntax or format detail beyond the schema, so the baseline 3 applies.

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 (schedule a reminder message), the actor (Telepath bot) and the recipient scope (authenticated account owner only). It also explicitly distinguishes the tool from a close sibling ("Does not create a Notes task"), so an agent can separate it from kb_create_note without opening either 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 an explicit gating condition ("only when requested or accepted by that user") plus two negative boundaries (no Notes task, no other recipient). It also tells the agent how to proceed under ambiguity ("Clarify the reminder text, time and timezone when ambiguous") and how to report outcomes ("Confirm scheduling only after success").

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