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

With no annotations, the description carries the full burden and does so well: it discloses validation rules (min 100x100px, aspect 1:4–4:1), accepted formats, a 10MB size cap, the storage/mutation behavior, the exact return shape {url,width,height}, and an auth note ('works before login too'). This is unusually rich behavioral context.

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 the core action and information-dense, with each clause carrying a distinct fact (formats, limits, downstream usage, auth). It is a long single paragraph rather than split into scannable structure, but there is little 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?

For a mutation tool with no annotations and no output schema, the description covers everything needed: input alternatives, validation constraints, formats, size limit, return values, downstream usage, and auth behavior. An agent has all it needs to invoke 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 decision value beyond the schema: it labels file_path as 'preferred', presents data_base64 as the alternative, and pairs it with filename based on extension. That guidance on which parameter to choose is not in the schema.

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 ('Upload a product photo to AdGPT') with clear scope ('from the local machine'). It is immediately distinguishable from siblings like adgpt_image_resize or adgpt_single_asset, which do different things.

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 usage guidance: file_path is preferred, data_base64 is the alternative that requires filename, and the returned url belongs in user_instructions.uploaded_images when creating a campaign (max 5). It does not explicitly contrast against sibling tools, but the context for correct invocation is clear.

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