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

Annotations already declare the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=true). The description adds real behavioral context beyond them: the result is saved as a new image in the Xenition library and the original is retained. It does not mention prompt requirements per operation or async/latency 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?

Two tight sentences, front-loaded with the trigger condition and followed by the side effect. No filler and no repetition of the schema.

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 mutation tool with an output schema, the description covers the key facts an agent needs: when to use it, what operations exist, and that the original is preserved. Minor gaps remain around which operations require a prompt and any processing latency.

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 75%, so the schema already documents image, prompt and operation. The description still adds value by mapping user intent ('upscale', 'remove the background', 'make a variation') onto the operation values, helping the agent pick the right operation string. It says nothing about the undocumented 'title' parameter.

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 states a concrete verb and resource ('edit an existing image') and then enumerates the supported operations, which cleanly separates it from create_image (new images) and edit_video (video). An agent can route here without opening any 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?

The opening clause gives an explicit trigger: 'when the user wants an existing image changed', which implicitly excludes generation of new images. It never names a sibling alternative (e.g. create_image) or states exclusions explicitly, so it stops short of a 5.

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