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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: the course-not-found response, the 'always free' price with service level and replacement policy, and the content.available flag indicating whether module text is retrievable through this server. It doesn't contradict annotations.

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 dense paragraph that front-loads the core purpose and then lists the return fields. It's longer than ideal but every sentence adds information about the return payload or behavior. The structure is logical: purpose, return contents, error case.

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?

Given the output schema exists, the description doesn't need to explain return values in detail, but it does anyway, which is helpful. It covers the error case, the price/service policy, and the content availability flag. For a read-only, single-parameter tool, this is complete.

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%, so the schema already documents the slug parameter well. The description adds a useful cross-reference to listCourses as the source of the slug and gives an example ('seo-geo'), which helps the agent understand the expected format beyond the schema's regex-like description.

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 states a specific verb ('decide whether a course fits a learner') and resource ('one course'), and enumerates the exact data returned. It clearly distinguishes itself from siblings like getCourseModules and listCourses by focusing on the pedagogical ficha of a single course.

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 implies when to use it: when evaluating a course's fit for a learner, and it explicitly notes the 'course not found' response. It doesn't explicitly name sibling alternatives or exclusion conditions, but the purpose is clear enough that an agent can infer when to choose it over listCourses or getCourseModules.

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