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

Annotations already declare it's a non-read-only, non-destructive, non-idempotent write operation. The description adds that it appends to the end of the module, that old Editor.js format is accepted and converted, that video is provider+id not iframe, and that unknown fields are dropped. This is useful behavioral context beyond annotations, though it doesn't cover permissions or errors.

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 dense and somewhat stream-of-consciousness with a raw JSON snippet inline. It's front-loaded with the key behavior (appends to end) but the formatting could be clearer. Every sentence adds some value, but the JSON example makes it bulky.

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 an output schema exists, return values needn't be described. For a mutation tool with 6 params and 0% schema coverage, the description covers the most complex parameter (document) well and notes video handling and unknown field dropping. It's missing guidance on `kind` enum, `is_required`, and `duration_minutes`, which would fully complete it.

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 0%, so the description carries the burden. It explains the `document` parameter's expected TipTap JSON structure and that Editor.js format is also accepted, which is crucial since the schema only says 'object'. It doesn't explain kind, is_required, or duration_minutes, but the document guidance is substantial.

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 makes clear it creates a lesson appended to the end of a module, and mentions the document format. It distinguishes itself reasonably from update_lesson and create_module by focusing on lesson creation. It doesn't explicitly compare to siblings, but the verb+resource is clear.

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 statement 'Урок встаёт в конец модуля' implies when to use it (adding a lesson to an existing module), and it points to get_lesson for node examples. However, there are no explicit when-not-to-use conditions or direct comparisons to update_lesson.

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