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

Annotations declare this is a non-read-only, non-destructive, non-open-world write, so the safety profile is already covered. The description adds meaningful behavior on top: the expected date format and that passing null clears rather than sets, which is a distinct state transition an agent must understand. It stops short of saying whether the value is overwritten, persisted immediately, or validated against the course schedule.

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?

A single sentence that front-loads the action and scope, then closes with the format and null case. Nothing is redundant with the title and nothing is wasted.

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 one-parameter mutation with no output schema and clear annotations, this is close to complete: action, scope, format, and clear semantics are all present. Missing only error behavior and any confirmation of what a caller observes after the change.

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 description coverage is 0%, so the description carries the param burden — and it does, supplying both the accepted format (YYYY-MM-DD) and the nullable semantics of examDate. The only gaps are validation behavior on malformed input and whether timezone/date boundaries matter.

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 (set) plus resource (exam date) plus scope (player's exam for the current course), and it explicitly defines both value modes: a YYYY-MM-DD date or null to clear. An agent knows exactly what state this tool changes 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?

The description makes the operating context clear — it acts on the 'current course', so the caller must first be scoped via something like switch_course — and it names the clearing mode. No sibling tool overlaps this capability, so no explicit alternative-routing is needed, but there is also no stated precondition or error guidance.

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