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

Annotations only give generic hints (readOnlyHint=false, destructiveHint=false, openWorldHint=true); the description adds two non-obvious behaviors: credit cost and asynchronous project-id return. Doesn't mention failure modes or file format constraints, but that's in the schema.

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 short, front-loaded sentences; cost and next-step routing are packed in without waste.

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?

Output schema exists so return values needn't be explained, and the async workflow handoff is stated. Missing only a note on input image requirements or failure cases, which is minor.

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 100% with detailed descriptions for name and image_file_path, so baseline 3 applies; the description adds no param-level detail beyond what the schema already provides.

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?

Specific verb + resource: colorizes a black-and-white or faded photo. It also states the input constraint (grayscale/faded), distinguishing it from edit_image or generate_image.

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?

States the cost (10 credits) and explicitly says it returns a project id for wait_for_image_project, which directs the agent's next step. No explicit when-not-to-use or sibling exclusions, but the input condition narrows applicability well.

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