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

Annotations already declare readOnlyHint, openWorldHint=false, and destructiveHint=false, so safety is covered. The description adds value beyond them by disclosing the timezone of returned windows and a fallback behavior for the agent when live availability is missing, though it says nothing about pagination or result shape.

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, front-loaded with the core capability and followed by the one exception rule. Every clause earns its place with no restatement of the title or schema.

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-optional-parameter read tool with no output schema, the description covers scope, timezone, the day cap, and the fallback path. The remaining gap is what a returned window looks like (slot format/ordering), which an agent might benefit from given no output schema exists, but the essentials are present.

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 the schema already documents `days` (default 7, max 21) and `start_date` (default today). The description's 'IN local time' note is the only added meaning, and it applies loosely to `start_date` interpretation, so this sits at the baseline.

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?

The description names the resource (open arrival windows) and the scope (next few days, up to 21, in local time), which is clearer than the title alone. However, the verb is implicit and it never distinguishes itself from siblings like request_appointment or check_service_area, so the agent must infer which one to pick.

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?

It supplies one concrete usage rule — if online availability is unavailable, ask the customer for a preferred day and time instead — which is a real decision point. But it gives no guidance on when to prefer this over check_service_area or request_appointment, so the when-to-use story is only partially covered.

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