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

With no annotations, the description carries the full burden. It discloses the constraint that content_type must match content_url and explains the module_id null behavior. However, it does not describe potential side effects, return values, authorization needs, or error conditions, leaving significant behavioral gaps for a create operation.

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 two sentences, front-loaded with the core purpose, and every sentence adds value. It avoids redundancy and extraneous detail, making it easy for an agent to parse quickly.

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 13-parameter tool with no output schema and no annotations, the description covers the essential behavior but omits guidance on most optional parameters. It is adequate for a basic invocation but incomplete for a fully informed agent deciding on optional fields like content_format, is_published, or content_json.

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 only 8% (only is_preview has a description), so the description must compensate. It does add valuable meaning for the non-obvious parameters: content_type/content_url matching (with a concrete youtube example) and module_id null semantics. However, it does not explain other parameters like content_json, content_format, sort_order, or duration_seconds, which remain underspecified.

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 clearly states the tool's action and resource: 'Add a lesson to a course.' This specific verb+resource phrasing distinguishes it from sibling tools like create_module or update_lesson. The additional context about content_type matching and module assignment further clarifies its scope.

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 clear guidance on how to use the tool for key parameters (content_type must match content_url, module_id=null vs. a module uuid from list_course_modules). It references a sibling tool for valid module IDs. However, it does not explicitly state when to use this tool instead of alternatives like update_lesson or create_module, so it stops short of full when/when-not guidance.

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