Comfy Agent has no API in its launch post: Sume Agent Completions does

Comfy's launch post for Comfy Agent, read on 2026-10-04, describes an agent you use inside Comfy: it is available to everyone in Comfy Cloud, coming to Desktop in a few weeks, and it spends Comfy Credits. The post says you can run up to five chats in parallel. It does not mention an API or an MCP endpoint, so this post does not claim there is none; it only says that the announcement does not describe one.

If your job is to call an agent from your own backend, Sume's Agent Completions is the documented route.

What does Sume offer instead?

Agent Completions runs the Sume Agent on an ad-hoc prompt with a sandbox, tools and media generation, started by an API key and needing no person at a screen. You send POST /v1/agent/completions and get back 202 and an agent.run receipt, not choices[]. The Sume docs call it async, not a chat drop-in. The page is Agent Completions.

How do the two compare?

What does a call look like?

generation_spend_cap_usd is required and has no default; a request without it fails with 400 invalid_request. The cap replaces the spend-approval prompt that the chat UI shows, because an unattended agent has no one to ask. Send an Idempotency-Key header so a retry returns the original receipt with idempotency_hit: true.

curl -sS -X POST https://api.sume.com/v1/agent/completions \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Idempotency-Key: promo-batch-001" \
  -H "Content-Type: application/json" \
  -d '{
    "instruction": "Write a 15-second product teaser script.",
    "generation_spend_cap_usd": 2
  }'

What are the gaps?

Keys created before the feature shipped lack the agent_completions:read and agent_completions:write scopes and get 403 insufficient_scope, so create a new key. Service-account keys cannot create completions. Streaming and a synchronous OpenAI-compatible wire are not available at this time, and assistant turns in messages[] are rejected. When the run ends, Sume sends one signed agent.run.terminal webhook if you set communication.webhook_url, as Run webhooks describes. Branch on outcome.

Credit models differ, so do not compare prices from this page. Read Comfy's launch post for its terms and Sume's pricing page for ours.