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

With no annotations supplied, the description carries the full burden; it usefully discloses geometry (72x16 front, 160x80 back), approximate character capacity, scroll behavior for long first lines, and that it returns an image. It does not say whether the text replaces current display content, how long it persists, or whether a connection/permission is required.

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 short sentences, front-loaded with the core action and then the geometry constraints. Every clause (sizes, line limits, scroll, return value) carries operational information an agent would otherwise have to guess.

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 9-parameter, no-annotation, no-output-schema tool, the description covers the essentials of the primary rendering path and substitutes for the missing output schema by stating an image is returned. It falls short only on persistence and interaction with existing display state, which matters for a display-mutating tool.

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 78%, just under the baseline-3 threshold, and the description compensates well: the per-display character budgets (~17 vs ~37 per line) give the agent concrete meaning for line1/line2 beyond their maxLength of 120/60, and the scroll note explains overflow behavior. Remaining parameters (logo, accent, urgent, led_color) are covered by schema descriptions rather than the tool description.

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 and resource ("Show a short status ... ASCII only") and names the target device, so the agent knows it renders text on the Bar. It does not explicitly differentiate itself from the sibling bar_status, which the phrase "short status" could be confused with, so it stops short of a 5.

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?

No when-to-use or when-not-to-use guidance is given relative to siblings such as bar_status, bar_progress, bar_image, or bar_clear. The only constraints stated are content limits (ASCII only, one or two lines), which are format rules rather than routing guidance.

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