postiz-mcp

postiz_upload_from_url

Upload media from a public URL by providing the link. Postiz fetches the URL server-side and returns an ID and path for use in post creation.

Instructions

Upload a media file from a public URL via POST /api/uploads/url. Postiz fetches the URL server-side, so this works for sources the MCP host can't reach. Returns { id, path } usable in postiz_create_post value[].image[]. Requires enableWrite.

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": {
      "url": "<url>"
    },
    "name": "postiz_upload_from_url"
  }
}

Input Schema

Name	Required	Description	Default
`url`	Yes	Public URL Postiz should fetch.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Apr 30, 2026

TDQS

A4.1/5.0

Behavior4/5

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

Without annotations, the description discloses the HTTP method, endpoint, server-side fetch nature, return format, and a prerequisite, which is transparent for a simple upload tool. Lacks error or rate limit info.

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?

Three sentences, each adding value. Front-loaded with the core action and endpoint. No unnecessary words.

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

Completeness5/5

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

For a single-parameter tool with no output schema, the description fully covers purpose, mechanism, return value, and prerequisite, making it complete.

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 already describes the only parameter (url) as 'Public URL Postiz should fetch.' The description adds minimal context about reachability, but schema coverage is 100%, so baseline 3 applies.

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?

Clearly states it uploads a media file from a public URL, explains the server-side fetch, and specifies the return format and usage in another tool, distinguishing it from siblings.

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

Usage Guidelines3/5

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

Provides implicit guidance by noting 'works for sources the MCP host can't reach' and mentions 'Requires enableWrite', but does not explicitly state when not to use or contrast with alternatives like postiz_upload_file.

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