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

readOnlyHint=true already tells the agent this is a safe read, so the bar is lower; the description still adds real value by naming the returned fields (status, progress rate, average score, time on course, completed units, per-section/per-activity breakdown), which matters because there is no output schema. It omits auth/scope requirements and behavior for a non-enrolled user, so not a 5.

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?

Two sentences, zero filler: the resource scope comes first, the returned payload second, and the API route is a compact trailing pointer. Every clause earns its place.

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?

With no output schema, the enumeration of returned fields is the key completeness contribution, and it is present. What remains missing — behavior when the user isn't enrolled, pagination or size of the section/activity breakdown — is minor for a read-only lookup.

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 100% and both parameters are documented there (user id or email; course slug), so the baseline of 3 applies. The description adds nothing about parameter format or accepted values beyond what the schema already states.

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+resource (user's progress in one course) and enumerates the payload dimensions, which cleanly separates it from siblings like list_user_courses (enrollments, not progress), get_course_grades (course-level grades), and get_user (profile). The appended REST route pins the exact resource addressed.

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?

Usage is implied by the scoping ('one course', a single user) but the description never says when to prefer this over get_course_grades, get_course_analytics, or list_user_courses, nor does it state prerequisites such as the user needing to be enrolled. Adequate, but the agent must infer routing from the name alone.

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