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

Annotations already declare it is a non-read-only, non-destructive, non-idempotent write. The description adds genuine behavioral value beyond that: it explains the clean remux-pipeline closure that yields a valid moov atom, which is important for understanding output integrity. Auth/rate-limit behavior is not covered.

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 tight sentences, front-loaded with the core action, then the correctness guarantee, then the return values. No filler; each sentence earns its place.

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?

There is no output schema, so the description's enumeration of return values (hostPath, sizeBytes, durationMs, codec/resolution) is exactly what an agent needs. Combined with the pairing to the start tool and the moov-atom note, nothing material is missing.

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 coverage is 100% and the single recordingId parameter is fully documented in the schema as 'recordingId returned by device_record_start'. The description adds no syntax or format detail beyond what the schema provides, so the baseline 3 applies.

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+resource ('Stop a screen recording') and explicitly ties it to its counterpart 'device_record_start', distinguishing it from the many other stop/record siblings. An agent can identify the tool's role immediately.

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?

Clearly positions the tool as the termination of a flow begun by device_record_start, giving strong implied context for when to call it. It doesn't state explicit exclusions or what to do if no recording is active, so it stops short of a 5.

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