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

Annotations declare the mutation and open-world profile, and the description adds context they don't carry: exactly one photo per call (implying repeated calls for multiple images) and a hard availability limit by store platform. It does not address what happens when the fetch fails or whether a re-call duplicates the image, so it stops short of full disclosure.

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?

Three short sentences, front-loaded with the action, then the usage trigger, then the platform exclusion. Nothing is redundant with the title or 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 two-required-parameter mutation with no output schema and safety already covered by annotations, this tells an agent what it does, when to reach for it, and where it will fail outright. Only the post-call behavior (return value, failure/duplicate handling) is unaddressed, which is a minor gap given the annotation coverage.

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%, and the schema already documents the URL constraints (PNG/JPEG/WebP, 15 MB) and that product_id is a UUID from list_products. The description only echoes 'public image URL' and adds no format or sourcing detail beyond the schema, so baseline 3 applies.

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 (adds one photo to a product) plus the source (a public image URL). The word 'one' scopes it as a single-image operation, which separates it from any bulk sibling, and it names the store-type restriction outright.

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 an explicit trigger ('use it when a product has none suitable') and an explicit exclusion with a redirect ('Not available on Shopify stores: add photos to the product in Shopify instead'). Both the when and the when-not are stated, not inferred.

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