Can hosted MCP run a Sume Format? Call it over REST with an API key

Short answer

No. As of 2026-10-08 the tools-and-gates page for Sume's hosted MCP at https://mcp.sume.com/mcp lists no tool that starts a Format run. To run a Format, call the REST endpoint POST /v1/formats/{handle}/{slug}/runs with an API key that has the formats:write scope and an Idempotency-Key header.

That is a deliberate split, not a gap in your connector. MCP covers jobs, assets, text to speech, avatars, crawl and account reads. Formats run through the Format API, where the receipt, version pin, webhooks and spend cap are defined.

What to use for what

The table maps common tasks to the surface that supports them.

Using both in one agent

An agent can hold two credentials. Give it the MCP connector for exploration and job waiting, and give your own backend the REST key for starting Format runs. The agent asks your backend to start a run, and the backend returns the run id.

Do not look for a Format inside script_run. That tool only calls tools that appear in the MCP registry, so it cannot reach a Format run either.

Check it yourself

Call tools_list on your own connection and search the names for anything Format-shaped. Under OAuth with Write off the list is shorter still. The registry is the source of truth, and the docs warn not to assume parity with the HTTP API.

Then send a run over REST. A fresh run answers 202; replaying the same key answers 200 with the same receipt.

curl -sS -X POST https://api.sume.com/v1/formats/sume/sume-slideshow/runs \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Idempotency-Key: demo-slideshow-2026-10-08-001" \
  -H "Content-Type: application/json" \
  -d '{"instruction":"Three slides about our spring sale.","generation_spend_cap_usd":20}' | jq '{id, status}'

Credentials and scopes for the REST side

A Format call needs formats:write to start a run and formats:read to read the receipt or list Formats. Service-account keys are refused for Formats, and a team Format needs a key issued in that workspace, otherwise you get 403 workspace_key_required. Keep this key on your server. Do not paste it into an MCP client config, where an agent could echo it.

The key also decides which wallet pays. The run is billed to the workspace the key belongs to, and no tool argument can change that.

A pattern that works

Have your backend start the run, store the returned id, and register communication.webhook_url so Sume tells you when it ends. Meanwhile an MCP-connected agent can read assets or crawl pages the Format will use. When the webhook fires, the backend fetches nothing more unless the payload is null for size, in which case it reads error.result_url.

This keeps the paid, versioned, auditable step in code you control, while the agent keeps the flexible read-only work.

Document the decision in the repository next to the code that makes the call, so the next engineer sees why the choice was made and which docs page it came from. Re-read that page when you upgrade a client or change a key, since gates and limits are the parts most likely to differ from what you remember.

A short note of the date you last verified the behaviour, such as 2026-10-08, is enough for a reviewer to know how fresh the claim is.

• Start: REST with Idempotency-Key.
• Observe: webhook, or GET /v1/format-runs/{id}.
• Explore: MCP read tools.