add_image_watermark_to_image

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

No annotations are provided, so the description must disclose behavioral traits. It adds useful context such as opacity range (0.0–1.0), position enums, custom x/y, rotation in degrees, and optional output path, but it does not explain whether the source image is modified, the output file format, or potential side effects. This leaves some ambiguity.

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 a single, information-dense sentence. It front-loads the core purpose and then enumerates required and optional parameters efficiently. It could be slightly better structured (e.g., separating required vs. optional), but no sentence is wasted.

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 13-parameter tool with no output schema and no annotations, the description covers most parameter semantics and gives some ranges, but it lacks important contextual information: what the output looks like, whether the original file is overwritten, any prerequisites (e.g., file formats, permissions), and how it fits with sibling tools. It is adequate but has clear gaps.

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 0%, but the description explicitly names most parameters (image_file_path, watermark_image_file_path, position, opacity, offsets, position_x/y, rotation, output path) and adds meaning beyond the schema: it lists all allowed position values, clarifies that position_x/y are for 'custom', and gives an opacity range. Some output-related parameters (doc_name, output_dir, output_file_name, watermark_file_name) are only vaguely covered by 'output path'.

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 overlays a watermark image on a source image, using a specific verb ('Overlay') and resource ('watermark image on a source image'). It also names the API endpoint. This distinguishes it from sibling tools like add_text_watermark_to_image.

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 use for image watermarks and lists all required parameters and position options, but it does not explicitly state when to use this tool versus alternatives such as add_text_watermark_to_image or add_image_stamp_to_pdf. There are no clear exclusions or alternative pointers.

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