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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered structurally. The description adds genuinely new material beyond that: the NOT_FOUND failure mode and the recommended next call. It stops short of describing the returned schedule shape or what 'default availability' contains.

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?

Two short sentences, zero filler, with the failure/next-step information front-loaded right after the purpose. Nothing could be removed without losing 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?

For a zero-parameter read tool with read-only annotations, the definition covers purpose and the main edge case, which is most of what an agent needs. Since there is no output schema, it leaves the caller without any hint of what a schedule object contains, a minor residual gap.

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?

The tool takes zero parameters and the schema is an empty object, so there is nothing for the description to disambiguate. Baseline of 4 applies; the added clause about the missing-schedule case is a bonus rather than a parameter concern.

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?

Specific verb+resource ('Fetch the user's default availability schedule') with a scope qualifier — 'default' — that separates it from get_schedule, get_schedule_by_user, and list_schedules in the sibling list. An agent can tell this returns the caller's own default rather than an arbitrary schedule by ID.

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 handles the empty-state branch well by naming the follow-up (create_schedule), but it never states when to prefer this over the many other schedule readers (get_schedule, get_schedule_by_user, list_schedules). Usage is implied by 'default' rather than explicitly contrasted with alternatives.

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