image_diff_stats

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

No annotations are provided, so the description carries the full burden. It discloses the return values (statistical metrics) and implies a read-only operation, but does not explicitly state that the tool does not modify files or require special permissions. The warning about catching unintended changes adds some transparency, but more explicit statements about safety and side effects would improve it.

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 two sentences with a line break, each sentence adds value. It is front-loaded with the core purpose and includes a memorable phrase ('I changed only what I meant to' gate) that helps recall. No extraneous information.

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 description covers the main return values and the relationship with a sibling tool. However, it fails to address how the optional subfolder parameters affect behavior or defaults. Since an output schema exists (not shown), the return structure can be assumed documented, but parameter usage context is missing.

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%, meaning the input schema lacks descriptions for all 4 parameters. The description does not mention any parameter names, purposes, or usage details (e.g., what filename_a and filename_b refer to, or how subfolders work). For a tool with 4 parameters and no schema descriptions, the description must compensate, but it provides zero parameter guidance.

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 that the tool quantifies change between two image passes, returning mean/max absolute difference and percentage of pixels changed. It differentiates from the sibling CompareImages by explaining that CompareImages shows what changed while this tool shows how much, and it warns about detecting unintended large changes.

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 explicitly recommends pairing with compare_images and explains the complementary roles (what vs. how much). It does not provide explicit when-not-to-use scenarios, but the context is sufficiently clear for an AI agent to decide when to invoke this tool over alternatives.

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