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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds useful return-content context by listing the four fields the agent can expect. It does not mention error behavior, permissions, or what happens when a slug is invalid, but that is minor for a simple read tool.

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?

The description is a single compact phrase with no wasted words and the key output fields are front-loaded. The lack of an explicit verb makes it slightly awkward as a sentence, but it remains quickly scannable and informative.

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, read-only tool, the description plus annotations and schema cover the essentials. There is no output schema, so the field list meaningfully compensates. The implicit 'returns a module by slug' behavior is clear from the title and required parameter.

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?

The single parameter slug has 100% schema coverage with a clear example, so the schema carries the parameter semantics. The description adds no special parameter meaning beyond implicitly referencing the module lookup. This matches the baseline for high schema coverage.

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 identifies the resource (a module) and the specific fields returned: description, duration, access level, and section list. It lacks an explicit verb, but the title 'Get a module' disambiguates the action. It does not explicitly contrast with sibling tools like list_modules, so differentiation is only implicit.

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 provides no guidance on when to use this tool versus alternatives such as list_modules or read_lesson. There are no usage conditions, exclusions, or alternative routing. The need for a slug is only implied by the schema, not the description.

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