Mini App Hub

by dev.workers.miniapp-web.ecosystem-task-gateway

watermark_document

Add clean diagonal watermark text to PDF or Image files.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "fileUrl": "<fileUrl>",
      "watermarkText": "<watermarkText>"
    },
    "name": "watermark_document"
  }
}

Input Schema

Name	Required	Description	Default
`fileUrl`	Yes	File URL
`opacity`	No
`watermarkText`	Yes		CONFIDENTIAL

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 5, 2026

TDQS

C2.7/5.0

Behavior2/5

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

No annotations are provided, so the description carries the full behavioral burden. 'Add' implies a mutation, but it never says whether the source file is overwritten or a new file is returned, where output goes, or what permissions are required — significant gaps for a write operation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

A single tight sentence with the action and target front-loaded and no filler. It is appropriately sized, though it is arguably too short given the surrounding unknowns.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a mutation tool with no annotations, no output schema, and two undocumented parameters, the description should explain overwrite behavior, output format, and opacity meaning. None of that is present, leaving the agent unable to predict the tool's effects.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is only 33% (just 'File URL'), and the description does not compensate. 'Diagonal' hints at a placement option that is not even a parameter, while 'opacity' and the watermark text default are left entirely to the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Add ... watermark text to PDF or Image files'), which cleanly separates it from the sibling compression and conversion tools. It does not name a sibling explicitly, but the resource is unambiguous enough that differentiation is not needed.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance on when to use this versus alternatives, no prerequisites (e.g. file size limits or supported formats), and no exclusions. The agent must infer all usage context from the name alone.

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

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