openwebui-mcp-server

openwebui_create_function

Create Pipe, Filter, or Action functions in Open WebUI with Python code. Add model options, transform messages, or add chat buttons.

Instructions

Create a new Pipe, Filter, or Action function in Open WebUI. Pipes add new model options. Filters transform messages. Actions add chat toolbar buttons. Provide valid Python code.

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": {
      "id": "<id>",
      "name": "<name>",
      "type": "<type>",
      "content": "<content>"
    },
    "name": "openwebui_create_function"
  }
}

Input Schema

Name	Required	Description
`id`	Yes	Unique function ID (lowercase, underscores only, e.g. "my_summarizer_pipe")
`name`	Yes	Human-readable display name
`type`	Yes	"pipe" — adds a new model option; "filter" — transforms messages; "action" — adds chat button
`content`	Yes	Python source code for the function
`description`	No	Optional description shown in the UI

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.2Aug 10, 2026

TDQS

A3.9/5.0

Behavior3/5

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

With no annotations, the description must carry the burden of behavioral disclosure. It states 'Create' (mutation) and 'Provide valid Python code,' hinting at code validation. It also explains what each function type does behaviorally. However, it does not mention error handling, permission requirements, return values, or side effects, which are significant gaps for a mutation tool without annotations.

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

Conciseness5/5

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

The description is three sentences: the first states the primary purpose, the second explains the three types, and the third reminds about valid code. Every sentence earns its place, no redundancy, and the most important information is front-loaded. This is appropriately concise and well-structured.

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

Completeness3/5

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

The tool is a straightforward create operation with no output schema and no annotations. The description explains the function types and the need for valid code, but it does not describe the return value, potential errors, or any post-creation steps. For a CRUD create tool, this may suffice, but the absence of any outcome/response info leaves some ambiguity for an agent.

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

Parameters3/5

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

Schema coverage is 100%, so the schema already documents all parameters. The description repeats the type meanings already present in the schema enum descriptions, adding no new information. It does reinforce the requirement for valid Python code in the 'content' field, but this is marginal beyond the schema's own description. Baseline 3 is appropriate.

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

Purpose5/5

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

The description opens with a specific verb+resource: 'Create a new Pipe, Filter, or Action function in Open WebUI.' It immediately distinguishes from sibling CRUD tools (update, delete, list, get) and clarifies the three function categories with their purposes. This is a clear, non-tautological statement of purpose.

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

Usage Guidelines4/5

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

The description gives clear context on when to use each function type (pipe/filter/action), which helps the agent choose the correct 'type' parameter. However, it does not explicitly mention alternatives like update_function for existing functions, so the when-not guidance is missing. The intent is obvious from the name, so this is clear but not fully explicit.

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