compare_renders

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

With no annotations provided, the description carries the burden of explaining behavior. It states the input type, the comparison operation, and the output, which is useful but minimal. It does not disclose prerequisites, whether the operation is read-only, how channels affect the comparison, or what happens on mismatch/error.

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 that front-loads the core action and output. Every word earns its place, with no filler or redundancy.

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?

The tool is simple and has an output schema, so return-value details are not required. However, the missing documentation for the channels parameter and the lack of usage guidance or alternative routing make the description only minimally complete for correct invocation.

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 0%, so the description must compensate. It clarifies that reference and candidate are completed job IDs or image paths, but it does not explain the 'channels' parameter at all, even though it has a default of 'R,G,B' and is likely important for the comparison. This leaves one of three parameters effectively undocumented.

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 the action ('Compare two completed job IDs or image paths') and the result ('return a difference image'), so an agent knows what the tool does. It does not explicitly differentiate from sibling tools like run_comparison_manifest, but the purpose is specific enough to avoid confusion.

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 when to use the tool: when two completed job IDs or image paths need to be compared and a difference image is desired. However, it does not provide explicit guidance on when not to use it or mention alternatives such as run_comparison_manifest, leaving some inference to the agent.

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