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

Beyond the annotations, the description discloses real behavior: timezone resolution to UTC, refusal of ambiguous or nonexistent DST times, and the exact UTC ISO seconds format for createdAt. This is exactly the kind of error-condition and normalization detail an agent needs before invoking a converter.

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?

Dense but front-loaded: purpose first, then input format, then behavior and the negative-scope caveat. It packs a lot into a few clauses with little waste, though the single unbroken paragraph is slightly hard to scan.

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-parameter converter with an output schema present, the description covers purpose, input grammar, timezone handling, failure modes, and the absence of calendar side effects. Nothing an agent needs to call 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?

With 0% schema description coverage, the description must carry parameter meaning, and it does: eventBrief is decomposed into Start/Duration/Title components plus an optional Markdown heading, and createdAt's UTC-seconds requirement is stated. It stops short of describing edge cases like maxLength (131072) or what happens with malformed briefs.

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 opens with a specific verb+resource ("Create a real iCalendar file from a brief") and immediately details the exact shape of the input. It is clearly distinguished from the file-conversion siblings and from any tool that would actually place an event on a calendar.

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 scope statement "Does not add any calendar event" usefully clarifies that this only produces a file artifact, but the description never states when to pick this tool versus an alternative or what preconditions apply. Usage is implied by the detailed brief format rather than explicitly guided.

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