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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely new behavioral context by explaining that classification is derived from course start/end dates rather than a stored status field, which explains why a course may appear in an unexpected bucket.

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?

Three short lines, front-loaded with the operation, then the alternative and the practical question it answers. No restatement of the tool name and 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?

An output schema exists and annotations cover read-only semantics, so the description need not explain return values. For a one-optional-parameter read tool, what remains — what it lists, how it filters, and its sibling's role — is fully covered.

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% and the single enum is already fully documented, so the baseline is 3. The description earns the extra point by explaining the underlying criterion (start/end dates) that determines which classification a course falls into, which the enum labels alone do not convey.

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?

States a specific verb and resource (list enrolled courses) plus the exact filtering axis (Moodle's own timeline classification based on start/end dates). It explicitly contrasts itself with list_courses ('returns everything unfiltered'), so an agent can pick between the two without opening either 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?

Names the alternative (list_courses) and the condition that selects this tool, with a concrete intent phrase ('what am I actually taking right now'). It does not mention search_courses or state when this tool should NOT be used, so it falls just short of fully explicit routing.

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