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

Goes well beyond the readOnly/idempotent annotations: discloses that it performs GET requests to public shop prices and the download URL, that only the file header is read, and that the photo is never stored or uploaded and no order/payment is created. This is exactly the extra context annotations cannot carry.

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?

Front-loaded with purpose, then usage, then behavior and return values, and every sentence adds information. The trailing Dutch sentence largely duplicates the opening purpose statement, which is the one bit of 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?

With no output schema, the description fully covers what comes back (recommended size, alternatives, crop share, live price per size) and the side-effect profile. For a 5-parameter nested-input tool, an agent has everything needed to call it correctly.

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 baseline is 3, but the description adds meaning: width/height are in pixels, the photo object is only header-read, and it clarifies that pixel dimensions and a photo/URL are interchangeable inputs. It does not mention wanted_size, so it stays just above baseline.

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?

States a specific verb and resource: 'size and price advice for a custom diamond painting kit made from the customer's own photo'. It is clearly distinct from the siblings (search_products, shop_info), which deal with catalog and shop data rather than per-photo advice.

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?

Gives concrete trigger questions ('whether their photo is suitable, which canvas size fits, or what a kit of their own photo costs') and boundaries ('measures resolution and aspect ratio only, not sharpness or lighting'). It does not explicitly name alternatives, but the siblings are unrelated enough that this is a minor gap.

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