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 fully covered. The description adds no behavioral context beyond 'fetches one course by id' – it doesn't mention 404 behavior, whether the course includes nested content, or any rate limits. With annotations covering the key traits, a 3 is appropriate.

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?

One short sentence, front-loaded with the verb and resource. Zero wasted words. The description is appropriately minimal for a simple getter.

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 simple single-resource getter with one fully-documented parameter, an output schema, and annotations covering safety/idempotency, the description is nearly complete. It could mention what happens when the id doesn't exist (404 vs empty), but that's a minor gap given the output schema exists.

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% – the id parameter is fully described in the schema ('The course id, as returned by list_courses or create_course'). The description adds no additional parameter meaning beyond what the schema provides. Baseline 3 is correct.

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 'Fetches one course by id' clearly states the verb (fetches), the resource (one course), and the identifier (id). It is distinct from list_courses (which fetches multiple) and update_course/delete_course (which mutate). However, it doesn't explicitly differentiate itself from other get_* siblings, though the resource name makes that obvious.

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 usage: call when you need a single course by id. It doesn't explicitly state when not to use it or mention alternatives like list_courses for multiple courses. The context is clear enough for a simple getter, but no explicit guidance is given.

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