给图片加文字水印（1 credit/次）。中文水印无需系统字体；产物存文件中转站返下载 URL。失败自动退款。
| Name | Required | Description | Default |
|---|---|---|---|
| to | No | 输出格式 png/jpeg/webp；缺省跟随源格式 | |
| text | Yes | 水印文字（中英文均可，最长 64 字符） | |
| color | No | 文字颜色(#hex 或颜色名)，默认 #888888 | #888888 |
| file_id | No | 已上传的图片 ID（与 data_base64 二选一） | |
| opacity | No | 不透明度 1-100，默认 35 | |
| filename | No | 可选输出文件名 | |
| position | No | 位置：center/top-left/top-right/bottom-left/bottom-right/tile(30°斜排平铺) | bottom-right |
| font_size | No | 字号(px)；缺省按图宽自动 | |
| data_base64 | No | 图片内容 base64（与 file_id 二选一） |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are present, so the description carries the full transparency burden. It discloses pricing (1 credit/call), output storage and URL return, failure refund policy, and a font-system prerequisite for Chinese text. It does not mention whether the source image is modified or if the returned URL expires, but the key side effects are covered.
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?
A single compact sentence conveys purpose, cost, font requirement, output mechanism, and failure handling. Every clause earns its place and nothing redundantly repeats schema content.
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?
Given the absence of an output schema and annotations, the description provides the essential contract: what the tool does, how output is delivered (download URL), cost, and failure refund. It could explicitly restate the file_id/data_base64 either-or requirement, but the schema already documents that, so the description is adequate for a 9-parameter 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 coverage is 100%, so the baseline is 3. The description adds value beyond the schema by noting that Chinese watermark text does not require system fonts, which removes a practical concern for the required 'text' parameter. All parameter details are otherwise fully documented in the schema.
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 opens with '给图片加文字水印' (add text watermark to image), a specific verb+resource phrase that unambiguously identifies the tool's function. This distinguishes it clearly from sibling image tools like img_compress, img_convert, and img_crop.
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 does not explicitly contrast this tool with alternatives or state when to prefer it. It does offer operational context—Chinese watermarks don't need system fonts, output goes to a transfer station, and failures auto-refund—but the usage scenario is only implied by the purpose.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Most tools are clearly distinct, but img_compress and img_convert both support format changes, and img_info and img_exif both read metadata, creating minor overlap. The descriptions help clarify the primary purposes, so ambiguity is low.
All tools share the img_ prefix and mostly use verb-based names like img_compress and img_resize. However, img_info and img_exif are noun-based, which is a slight deviation from the pattern, though still predictable and readable.
With 8 tools, the server is well-scoped for an image toolbox. Each tool addresses a common operation without unnecessary additions, making the count appropriate for the stated purpose.
The toolset covers the core image lifecycle: inspecting info, reading EXIF, compressing, converting, resizing, cropping, rotating, and watermarking. There are no glaring gaps for a practical image toolbox, so agents can handle typical workflows end-to-end.