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

With no annotations, the description must carry the behavioral load. "Right now" and "as an image" usefully convey that this is a non-mutating snapshot returned in image form, but it says nothing about connection prerequisites (e.g. bar_connect), error behavior when the bar is offline, or how the image is delivered in the response.

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?

A single front-loaded sentence with no filler. Every element (action, target, timing, output type) 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?

For a one-parameter read tool with no output schema, the description covers the core intent but omits practical details an agent would want: whether the device must be connected first, how failures surface, and the image format/encoding returned.

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 parameter is fully documented in the schema, including enum values, default, resolution, and color depth for each display. The description adds no additional parameter meaning, so the baseline of 3 applies when the schema does all the work.

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?

"Grab what a BUSY Bar screen shows right now, as an image" names a specific verb (grab), a specific resource (current screen contents), and the output form (image). That is enough to separate it from siblings like bar_status or bar_image, though it never names an alternative explicitly.

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?

There is no when-to-use guidance and no mention of alternatives such as bar_status, which also reports device state. The phrase "right now" hints that this is a point-in-time capture rather than a status read, but the agent must infer that distinction on its own.

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