n8n File Conversion with the MCP Client Tool Node

n8n's AI Agent node can call tools exposed by MCP servers through the MCP Client Tool node. Pointed at file-convert.online, that gives an n8n workflow the ability to convert documents, images, audio and video without a custom HTTP integration. This walkthrough builds a workflow that receives a file URL, converts it, and delivers the result.

What you need

• An n8n instance (cloud or self-hosted) recent enough to include the MCP Client Tool node with the HTTP Streamable transport.
• A file-convert.online account and an API key (fc_live_...), created at file-convert.online/account/api-keys.
• A chat model credential for the AI Agent node (any provider n8n supports).

Step 1: add and configure the MCP Client Tool node

1. Add an AI Agent node to the canvas and attach a chat model.
2. Attach an MCP Client Tool node to the agent's Tools input.
3. Endpoint: https://file-convert.online/api/mcp/v1/mcp
4. Server transport: HTTP Streamable.
5. Authentication: Bearer. Create a new Bearer credential and paste the API key. Older n8n versions expose the same thing as a Header Auth credential with name Authorization and value Bearer fc_live_....
6. Tools to include: all. The server exposes eight; you can restrict the agent to convert_file, get_job_status and get_download_url for a narrow workflow.

Open the node's test panel; it should list the tools. A 401 here means the credential value is not exactly Bearer, a space, and the key.

Step 2: give the agent a job

A system prompt like the following keeps the agent on rails:

You convert files with the fileconvert tools.
Input: a file URL, its current format and the target format.
1. Call convert_file(source_url, source_format, target_format).
2. Call get_job_status(job_id) every 3 seconds until status is Completed or Failed.
3. On Completed call get_download_url(job_id) and return the download_url.
4. On Failed return the reason. Never invent a URL.

Feed the user message from the trigger, for example a Webhook node receiving {"url": "https://.../deck.pptx", "from": "pptx", "to": "pdf"}.

Step 3: deliver the result

The download URL works without authentication (the unguessable file id is the capability), so add an HTTP Request node after the agent: method GET, URL from the agent output, response format File. Then hand the binary to whatever comes next: a Google Drive, S3, Slack or email node. Results stay downloadable for about an hour, which is plenty for a workflow that runs immediately; for delayed delivery, call the REST retention endpoint described in the README.

Local files instead of URLs

When the trigger delivers a binary (an email attachment, a form upload), the agent path is upload_file followed by start_conversion. Base64 in the model context is fine for small files but wasteful for large ones, so the cleaner pattern is to upload with an HTTP Request node yourself (POST https://file-convert.online/api/file/v1/file, multipart field file) and pass the returned file id to the agent with the instruction to call start_conversion(file_id, source_format, target_format).

Batching and costs

A Split In Batches or Loop Over Items node in front of the agent converts a list one file at a time. Each conversion costs credits by category (1 for images, 2 for documents, audio, archives and ebooks, 5 for video); the agent can call get_balance at the start of a run and stop early when the budget is short. Rate limits are per minute and grow with the plan; a 429 is returned to the agent as an instruction to wait, and n8n's own retry settings on the agent node cover the rest.

Errors you may see

• "invalid api key": credential misconfigured or key revoked.
• "No conversion with job_id ... found": the agent hallucinated an id or reused one from another account. The system prompt above prevents most of it.
• "different categories": the agent asked for png to pdf. Conversions run within one category; pick the right target or convert in two steps where a bridge format exists.
• "no credits left": top up at file-convert.online/pricing or wait for the daily free package.

Everything the tools accept and return is documented in the README at file-convert.online/blog/file-convert-mcp-server-readme, and the REST twin of every tool is described at https://file-convert.online/api/mcp/openapi.json for workflows that prefer plain HTTP Request nodes.