Take a screenshot

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

Annotations declare readOnlyHint=false but give no reason; the description supplies that reason by disclosing the side effect — a file is written to /media/fat/screenshots. That is genuine added context beyond the structured fields. It stops short of saying what the call returns (image payload vs. path) or how the write failure is surfaced.

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, action first, side effect second, default behavior third. Nothing is padded and nothing needs re-reading.

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 zero-required-parameter tool with full schema coverage and a declared side effect, this is nearly sufficient. The one gap is the return shape — whether the agent gets image content back or just a file path — which is not covered by an output schema and is only implied by 'as an image'.

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 parameter is well documented as 'MiSTer name from get_status', so baseline would be 3. The description goes slightly beyond by explaining the runtime fallback behavior when host is omitted, which the schema only gestures at with 'omit when the call already says which'.

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: 'Capture what a MiSTer is showing, as an image.' No sibling tool (get_status, launch, backup_saves, etc.) overlaps with this action, and the description makes the distinction obvious without needing the 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?

'Without host, uses the one MiSTer that's running something' gives a clear condition for the host-omitted call path. There are no true alternatives among siblings, so no exclusions are needed, though it never explicitly says when to prefer this over, say, inspecting state via get_status.

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