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

With no annotations, the description must carry the behavioral burden, and it does disclose two genuinely useful facts: the credit cost of 1 and the return shape { processedImage }. It says nothing about permission/auth requirements, input size or resolution limits, whether a failed call still consumes credits, or whether the result is persisted as an artwork.

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, effect first, return value and cost immediately after — zero wasted wording and well front-loaded.

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?

This is a simple two-parameter tool whose schema is fully described and whose return value is stated in the description, so little is missing. The main residual gap is operational behavior around cost and failure, which matters somewhat for a credit-consuming tool.

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 description coverage is 100%, and the schema already documents both the base64/URL formats for image and the enum plus default for style. The description adds no parameter meaning beyond that, so the 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?

"Apply a retro look to an image" gives a specific verb and resource, so the effect is unambiguous. It does not, however, distinguish itself from visually adjacent siblings such as polaroid_transform, dslr_transform, or ai_filters, so an agent must infer the boundary itself.

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?

There is no when-to-use or when-not-to-use guidance and no named alternative; the description never says why an agent would pick this over polaroid_transform or ai_filters. Usage can only be inferred from the effect name.

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