Retrieve the color of a single pixel on a canvas by specifying X and Y coordinates, with an optional canvas name.
Get the color of a single pixel.
| Name | Required | Description | Default |
|---|---|---|---|
| x | Yes | X coordinate | |
| y | Yes | Y coordinate | |
| canvas | No | Canvas name | default |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are present, so the description has the full burden of disclosing behavior. It states that the tool reads a pixel's color, but does not explain the return format, coordinate bounds, invalid-pixel handling, or the meaning of the default canvas. An agent cannot predict the tool's output or failure behavior.
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?
The description is a single concise sentence with no filler, and the core action is front-loaded. It is appropriately short for a simple tool, though additional context could have been added without much cost.
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?
With no output schema and no annotations, the description needs to explain what the tool returns and how it behaves on errors or invalid coordinates. It does neither. The low complexity of the tool is offset by the absence of critical return-value information.
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 input schema covers 100% of the parameters with descriptions, so the baseline is 3. The description adds no extra parameter context beyond the concept of a single pixel, but the schema's own descriptions are sufficient.
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 clearly states a specific verb ('Get') and resource ('the color of a single pixel'), making the tool's read-only purpose immediately obvious. It is distinguishable from sibling mutation tools like set_pixel and fill_rect, though it does not explicitly name or contrast them.
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 description implies the tool is used when you need to read a pixel's color at given coordinates, which is enough for a basic inference. However, it provides no explicit guidance about when to prefer this over alternatives or what prerequisites exist, such as ensuring the canvas exists.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.