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

With no annotations at all, the description carries the full burden and does add real behavioral facts: a credit cost of 1, the identity of the returned field ({ processedImage }), and a hard constraint that at least one caption must be supplied. It stops short of stating whether a new artwork is persisted, whether the source image is modified, or any failure modes beyond the caption rule.

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: action, constraint, return value plus cost. Nothing is redundant and the core capability is 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?

For a simple single-image transform, the definition covers the action, the required-caption rule, the cost, and the return key despite there being no output schema. Only persistence/overwrite behavior and failure conditions are left unaddressed.

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 sentence "At least one caption is required" encodes a cross-parameter constraint that the schema cannot express — topText and bottomText are individually optional, so this is genuine added meaning an agent would otherwise get wrong.

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 ("Add classic top/bottom meme captions to an image"), which cleanly separates it from sibling generators like avatar_generator, poster_generator, or cartoonize that also take an image but produce different output.

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?

The description implies when to use it via the meme-specific framing and notes the caption requirement, but offers no explicit when-to-use/when-not guidance and does not point to any alternative for related image-text overlays.

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