compose_images

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions the implementation detail ('Uses PIL for precise positioning') and clarifies 'no AI needed,' which helps set expectations about deterministic behavior. However, it doesn't disclose important behavioral aspects like whether the operation is destructive to original images, what the output looks like, or any rate limits/authentication requirements.

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?

The description is perfectly concise - two sentences that each earn their place. The first sentence states the core purpose with examples, and the second adds important implementation context. No wasted words, and the most critical information 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 9-parameter tool with no annotations and no output schema, the description is somewhat incomplete. While it clearly states what the tool does, it doesn't describe the output (what gets returned), error conditions, or performance characteristics. The schema handles parameter documentation well, but the description could better address the tool's overall behavior and results.

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?

With 100% schema description coverage, the input schema already documents all 9 parameters thoroughly. The description adds minimal parameter semantics beyond what's in the schema - it implies positioning capabilities and mentions local image handling, but doesn't provide additional meaning about how parameters interact or typical use patterns.

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?

The description clearly states the tool's purpose with specific verbs ('overlay one image on top of another') and resources (images), providing concrete examples (watermark, logo). It effectively distinguishes from siblings like 'edit_image' or 'resize_image' by focusing specifically on image composition rather than general editing or transformation.

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 provides clear context for when to use this tool ('add watermark, logo') and mentions an alternative for local images ('Use upload_file for local images'), which is helpful. However, it doesn't explicitly state when NOT to use it or compare it to other image manipulation siblings like 'edit_image' or 'inpaint_image'.

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