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

The description adds value beyond annotations: it details the side effect of writing a marker timeline JSON, specifies the return fields (video path, duration, etc.), and covers the error case. Annotations indicate non-destructive mutation, which is consistent.

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: the first covers the action and side effect, the second lists return values and error case. Every sentence is necessary and front-loaded. No wasted words.

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 tool with one optional parameter and no output schema, the description covers the action, side effects, return values, and error condition. The only minor gap is the unexplained '§6' reference, which could be clarified.

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?

The single optional parameter session_id is fully described in the input schema. The description adds no new semantic information about the parameter beyond the schema, so it meets the baseline for high schema coverage.

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 stops an active recording, finalizes a .mov file, and writes a marker timeline JSON. It distinguishes from siblings like screen_record_start and screen_record_status. However, the cryptic reference '§6' may confuse an agent without additional context, slightly reducing clarity.

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 when an active recording is present and mentions the no_active_session error condition. It does not explicitly provide when-not-to-use or compare alternatives, but the context (with screen_record_start and screen_record_status) makes the intended use clear.

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