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

Annotations already establish this is a safe, idempotent, non-destructive, closed-world read. The description adds genuinely new behavior: the data is live from the calendar, each slot is 15 minutes, and results are emitted both in the requested IANA zone and as UTC ISO strings. It omits volume/pagination details, which keeps it out of the top band.

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 sentences, both load-bearing: the first defines the output, the second defines the format and the consuming tool. Scoping and return format are front-loaded with no filler.

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?

With no output schema, the description correctly supplies the return format (local + UTC ISO) and the purpose/consumer linkage. The only omission is any indication of how days_ahead bounds the result set.

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 only 50%: timezone is documented in the schema, but days_ahead has no description at either layer. The description usefully clarifies that timezone governs how returned times are expressed, but adds nothing about the days_ahead look-ahead window, so it only partially compensates for the gap.

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 a concrete resource (free 15-minute video-call slots) and its source (Felix's live calendar), which is unmistakably distinct from the sibling book_call that consumes the result. An agent can tell what this returns without opening the 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?

It links itself to book_call, making the discovery-then-booking workflow clear, but never states an explicit when-to-use condition or any exclusions (e.g., fallback if no slots exist). Clear context, no negative guidance.

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