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

Annotations only indicate readOnlyHint is false, so the tool is a write operation, which the description clearly states. It goes beyond annotations by disclosing retention ('12 months') and automatic deletion, which is valuable context for planning.

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?

Four sentences with no waste. The critical action verb is first, then params, then next step, then retention. Every sentence is clear and necessary.

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 with 2 params and clear output usage. It covers input, output, and retention. However, it doesn't specify failure modes or exact output format, but the output is referenced and sufficient for a simple upload.

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 defines the parameters. However, the description adds meaning by specifying the requirement of a public https link for image_url and that image_base64 is the base64-encoded file, which the schema only hints at.

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?

Identifies a specific verb+resource ('Store the photo that will be printed on the poster') and is easily distinguished from siblings like create_poster_checkout. Even though it is named upload_photo, the description goes beyond the name, clarifying that the photo is for a poster.

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?

Explicitly states the input alternatives (image_url or image_base64) and the expected next step ('pass to create_poster_checkout'). This helps an agent decide when to use this tool and how to chain it with siblings. No explicit exclusions are needed given the sibling scope.

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