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

Annotations already declare the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=false, idempotentHint=false). The description adds that the output is raster pixels rather than a semantic tree, which is meaningful context, but it says nothing about the temp-file lifecycle (the PNG is deleted after return unless keep is set) or that each call is a fresh non-idempotent capture. With annotations carrying safety, this is adequate but not rich.

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?

Two sentences with zero filler, and the primary use case is front-loaded ahead of the alternative routing. Every clause 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?

An output schema exists, so return values need not be explained, and the sibling routing handles the main ambiguity. The one gap is the side effect of writing and then deleting a temporary PNG, which is neither in the description nor obvious from the 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%, so device, keep, and directory are already fully documented in the schema. The description adds no parameter-level detail (e.g., what device ids look like or the interaction between keep and directory), 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 action (capture pixels) and its exact scope (the entire desktop), which is more precise than the tool name alone. It explicitly distinguishes itself from three named siblings, so an agent can route correctly without opening any schema.

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?

Gives an explicit trigger condition (user needs pixels for the whole desktop) and names the alternatives for adjacent cases: ui_snapshot/browser_snapshot for semantic inspection, screenshot_region for a single window, monitor, or rectangle. Both when-to-use and when-not-to-use are covered.

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