screen_snapshot

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

With no annotations, the description fully carries the burden of behavioral disclosure. It discloses the tool is read-only, specifies default behavior (onScreenOnly, limit), a platform restriction (TikTok blocks tree mode), search semantics, diff functionality, and a parallelism constraint. This is exhaustive for the given complexity.

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 extremely concise: four short sentences, each serving a distinct purpose (purpose, defaults, TikTok constraint, search behavior, diff, warning). It is front-loaded with the primary action and immediately provides differentiating context.

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 6 parameters and no output schema, the description covers defaults, platform constraints, search variants, diff, and a parallelism restriction. It lacks explicit mention of error handling or return format, but the combination of schema descriptions and tool description is sufficient for an agent to invoke the tool correctly.

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% already, so baseline is 3. The description adds value by clarifying default values (onScreenOnly=true, limit=40), the auto-enable of regex when search contains '|', and the purpose of showDiff. It does not repeat schema descriptions but augments them.

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 reads the screen and returns generation-scoped refs, positioning it as the 'PRIMARY read tool.' This distinguishes it from sibling tools like screen_window, screen_search, and screen_shot, which are alternative read tools.

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 explicit when-to-use and when-not-to-use guidance: it covers default parameter values, TikTok constraints (forced texts mode), search behavior (substring vs regex), comparison feature (showDiff), and a critical warning not to parallelize app acts. This leaves little ambiguity for the agent.

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