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

Annotations already convey idempotentHint=true, destructiveHint=false, and readOnlyHint=false. The description adds behavioral context by explaining the two modes (recurring weekly vs. one-off date blocks), which clarifies the underlying scheduling semantics. It does not contradict annotations and supplements them with useful information about how the tool interprets its inputs.

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 concise sentences, each earning its place. The first states the core function; the second distills key usage patterns. No fluff, no repetition of schema details, and front-loaded with the central verb.

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?

The tool has an output schema (so return values are covered), annotations, and a schema with full parameter coverage. The description adds the essential recurring-vs-one-off distinction, which is the main complexity. It doesn't explicitly address the 'type' parameter (available/blocked) but that is well-documented in the schema. Overall, sufficient for an agent to use correctly in most situations.

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?

While the schema has 100% parameter description coverage, the description adds meaning by explaining the relationship between dayOfWeek, date, and isRecurring. Specifically, it states that dayOfWeek+recurring=true is for weekly schedules and date is for one-off blocks. This goes beyond the schema's individual field descriptions, helping the agent assemble a correct request.

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 starts with a specific verb+resource: 'Add an availability window for a resource.' This clearly distinguishes it from sibling tools like set_staff_availability (which targets staff, not resources) and get_available_slots (which reads availability). The additional clause about recurring vs. one-off further clarifies the tool's exact scope.

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 gives explicit usage guidance: 'Use day-of-week + recurring=true for weekly schedules, or a specific date for one-off blocks.' This tells the agent exactly which parameter combinations to use for different scenarios. It doesn't mention when not to use the tool or name alternative tools, but it provides strong contextual guidance for common cases.

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