Capture a Playdate screenshot

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

The description adds useful behavioral details beyond the annotations: it states that the framebuffer dimensions are 400 by 240, that a new PNG file is created, and that 'Existing files are never overwritten.' This meaningfully clarifies the safety profile and output behavior, even though the annotations already hint the operation is not read-only.

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, front-loaded with the core action and resource, followed by a precise safety guarantee. There is no filler, and every sentence adds necessary information for correct invocation.

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 simple two-parameter tool with a full schema and output schema present, the description is complete: it states the operation, the output type, the file-creation semantics, and the no-overwrite guarantee. Nothing essential is missing for an agent to call it 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 description coverage is 100%, so the schema already documents both parameters well. The description reinforces that output_path must be a new PNG path and that overwriting is avoided, but it does not add substantial meaning beyond the structured parameter descriptions.

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 names a specific verb ('Capture'), a specific resource ('the 400 by 240 framebuffer'), and an explicit outcome ('to a new PNG path and return it as MCP image content'). It is clearly distinguishable from sibling tools like playdate_record, which would capture continuous footage rather than a single frame.

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 intended usage is clear: use this tool when you need a static screenshot of the Playdate framebuffer saved as a PNG. It does not explicitly name alternatives or provide exclusion criteria, but the describe action is unambiguous enough that an agent can infer when this tool is appropriate.

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