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

Annotations provide readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false. The description adds important behavioral context: supported formats, 25 MB limit, and 30-day deletion policy for unordered pictures. This exceeds annotation coverage, though it doesn't explain auth needs or rate limits.

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, well-structured sentence with zero waste, front-loading the core action and then listing constraints. Every clause earns its place.

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 tool with 2 optional parameters, no output schema, and annotations that cover safety, the description provides all necessary context: input methods, storage behavior, supported formats, size limits, and lifecycle policy. Nothing critical 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 coverage is 100%, so the schema already documents both parameters (file and image_url). The description adds format and size constraints but doesn't explain the difference between using 'file' vs 'image_url' beyond the obvious. Baseline 3 is appropriate when schema does the heavy lifting.

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 uses a specific verb+resource ('Fetches a picture', 'stores it for a design', 'reports its size') that clearly distinguishes it from siblings like create_design or get_design. It states the full scope of the operation in the first sentence.

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 for checking/uploading a picture, but doesn't explicitly say when to use this versus alternatives. There is no guidance on prerequisites or when-not-to-use, leaving the agent to infer the context.

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