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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description's 'Reports' verb is consistent. It adds modest context by listing the returned data fields, but does not describe behavior when no recording is active or any error cases. This is acceptable given the read-only annotation coverage.

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 a single, tightly worded sentence that front-loads the core purpose ('Reports whether a recording is active') before listing the returned attributes. There is no redundant or filler content, making it an efficient and well-structured definition.

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 read-only tool with one optional parameter and no output schema, the description covers purpose, returned fields, and parameter source through the schema. It does not specify return format or behavior when no recording exists, but those are minor gaps given the tool's low complexity and the safety annotations.

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% for the single optional session_id parameter, which is clearly explained as coming from screen_record_start and as optional for the active recording. The tool description adds no additional parameter meaning beyond the schema, so it meets the baseline for high 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 uses a specific verb and resource ('Reports whether a recording is active') and enumerates returned fields (session_id, elapsed_ms, output path, marker_count). This makes the tool's role as a status query clear relative to action siblings like screen_record_start and screen_record_stop, though it does not explicitly name an alternative.

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 as a status check but does not explicitly state when to use it instead of related tools like screen_record_start/stop. Some guidance appears in the schema parameter description (leave session_id out for the active recording), but the description itself lacks direct when-to-use or exclusion guidance.

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