How do I run Create a Presigned Upload URL with Codex MCP?

Codex can use medux_create_upload_url through Medux MCP to create a presigned upload URL and file reference for a direct client upload. The workflow identifies the exact inputs, reviews the tool arguments, monitors processing, and verifies the returned result.

Codex MCP tutorial · get-started

How to create a presigned upload URL with Codex MCP and Medux

Q: Which MCP tool does this tutorial use?

This workflow uses medux_create_upload_url . Review its arguments before approval and consult the API reference for the current contract.

Use Codex and Medux through MCP to create a presigned upload URL and file reference for a direct client upload. This guide covers input preparation, the approval gate, task monitoring, and a concrete output check.

POST/api/app/v1/upload_urls

Create a pre-signed upload URL and file reference for a direct client upload.

Open the Create Upload URL API reference →

Codex-specific workflow

Run Create a Presigned Upload URL as a Codex MCP task

Use the active workspace as the source of truth. Ask Codex to identify the source filename, media type, and upload purpose, select medux_create_upload_url, and keep the Medux task ID and returned output with the rest of the project. Naming the input roles and the expected result prevents an agent from guessing which file should be used where.

Codex prompt pattern

In this workspace, use medux_create_upload_url through Medux MCP to create a presigned upload URL.
First inspect and identify the source filename, media type, and upload purpose.
Show me the exact tool arguments before execution.
After the task completes, return the upload URL and Medux file reference and verify that the URL accepts the intended file and the returned file reference is saved for the next call.

Approval gate

Before approving the call, compare the selected tool, file or asset IDs, ordering, timing, and output settings with the request. If a local filename was mapped to an uploaded Medux file ID, keep that mapping visible so it can be audited later.

Result verification

Let Codex monitor an asynchronous task until it reaches a terminal state, then save or report the upload URL and Medux file reference. The final check is explicit: confirm that the URL accepts the intended file and the returned file reference is saved for the next call.

What this tutorial does

Medux operation

Create a pre-signed upload URL and file reference for a direct client upload.

Agent workflow

Codex selects medux_create_upload_url, presents the arguments for review, calls Medux, and reports the response.

Before you start

Authentication

Authentication is required via Authorization header.

Preconditions

Try it is available after login because the returned upload target is account-scoped.
Use this as the first step in most Playground and agent flows.

Prompt Codex

Start with a clear instruction that names the Medux operation and the intended inputs.

Use Medux to run Create Upload URL. Review the required inputs, call medux_create_upload_url, wait for the result if a task is returned, and report the output clearly.

Request fields to review

Confirm these values before approving the MCP tool call. The linked API page remains the source of truth for current limits and response semantics.

Field	Type	Requirement	Purpose
`extension`	string	Optional	File extension without a leading dot, such as mp4.
`media_type`	string	Optional	Media type used to validate the file extension and build the upload object path. Use a supported Medux media type and check the linked API reference for the current enum values.

Step-by-step workflow

Connect Medux MCP to Codex

Add the Medux remote MCP endpoint to Codex, provide an authorized credential, and confirm that the medux_create_upload_url tool is available.

Prepare the required inputs

Prepare the source files, asset IDs, text, or settings required by the operation. Upload local media first when the tool requests file IDs.

Ask Codex to run Create Upload URL

Use one direct instruction with the intended values. Codex should select the Medux tool and show the proposed arguments before execution.

Review and approve the tool call

Check that the tool is medux_create_upload_url and that each file ID, task ID, option, and output setting matches your request before approving it.

Check the Medux response

If Medux returns an asynchronous task, let the agent monitor it until completion; otherwise review the immediate response and save any result identifiers or output URLs.

Workflow recap

User goal
  ↓
Codex selects medux_create_upload_url
  ↓
Review inputs and approve the tool call
  ↓
Medux runs Create Upload URL
  ↓
Codex reports the response and output

Frequently asked questions

Can Codex use the Medux Create Upload URL API through MCP?

Codex can call the medux_create_upload_url Medux MCP tool to create a pre-signed upload URL and file reference for a direct client upload. This guide covers the required inputs, approval flow, result handling, and the matching API reference.

Which MCP tool does this tutorial use?

This workflow uses medux_create_upload_url. Review its arguments before approval and consult the API reference for the current contract.