Mark lesson complete

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

Annotations already declare idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety bar is lower. The description adds real value on top: it states the blast radius is limited to the caller's own progress bar and that no confirmation prompt is needed, which is exactly the risk information an agent needs before auto-invoking.

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, front-loaded sentences with no filler. The action, the undo path, and the safety rationale each appear once and in priority order.

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?

No output schema exists, but the tool returns a simple progress change, so the description needn't explain return values. It covers scope, undo, and safety; only minor gaps remain, such as whether the account must be a group member for the call to succeed.

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% – all three parameters are documented, including that `completed: false` marks it not done and defaults to true. The description restates the `completed` semantics but adds nothing about `group` or `lesson_id` sourcing beyond what the schema already says.

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 ('Mark a lesson done') plus an explicit scope qualifier ('in your own course progress, or undo it'). The 'your own progress' framing distinguishes it from lesson-authoring siblings like update_lesson or create_lesson without needing the 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?

Gives clear conditions for both directions of use ('Mark as done' equivalent, and `completed false` clears it) and reassures the agent it can run unattended. It stops short of naming a sibling alternative or stating exclusions (e.g. when to use update_lesson instead), so it isn't a full 5.

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