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

With no annotations, the description carries the full burden, and it does disclose two valuable behaviors: the return shape { processedImage } and a concrete cost of 2 credits. However, it says nothing about whether the source image/artwork is mutated, whether credits are charged on failure, rate limits, or error behavior — meaningful gaps for a paid mutation tool.

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 compact sentences: action first, return value second, cost last. Every clause earns its place and nothing is padded.

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 two-parameter tool with full schema coverage, the description covers action, output field, and cost, which is nearly everything an agent needs. The remaining gap is sibling routing — nothing tells the agent to prefer ai_replace or ai_expand in adjacent scenarios.

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%, so both parameters are already fully documented, including the red-brush marking convention and the maskDescription example. The description adds only the general concept of "marked objects," which does not meaningfully extend beyond the schema — 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+resource pair ("Erase marked objects from an image") plus the effect ("fill the space naturally"), which distinguishes it from generative siblings like ai_replace or ai_expand without naming them. It is clear what the tool does, though it does not explicitly contrast itself with the closest sibling.

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?

Usage is only implied: the agent can infer it should be used when an image already contains painted-over regions. There is no explicit when-to-use statement, no when-not-to-use, and no named alternative (e.g. ai_replace for substitution vs. removal).

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