KNO-10168: Document default Content-Type header for fetch and webhook steps

[cjbell]

Description

This PR adds documentation for the new default Content-Type: application/json header that Knock automatically adds to HTTP fetch steps and webhook channel steps when request bodies are present (implemented in https://github.com/knocklabs/switchboard/pull/4793).

What changed:

• Added "Default headers" section to fetch function documentation (content/designing-workflows/fetch-function.mdx)
• Added "Default headers" section to webhook overview documentation (content/integrations/webhook/overview.mdx)
• Both sections explain the automatic header addition, user override capability, and GET/empty body behavior

Why:
Users need to understand that Knock now automatically adds standards-compliant Content-Type headers to requests with bodies, and that they can override this behavior if needed.

Key points documented:

1. Content-Type: application/json is automatically added when a request body is present
2. Users can override by explicitly setting their own Content-Type header
3. No default header is added for GET requests or requests without bodies

Human review checklist

• Verify documentation accurately reflects the switchboard implementation behavior
• Check that the wording clearly explains the override mechanism
• Confirm the examples given (application/xml, text/plain) are appropriate
• Ensure section placement makes sense in the document flow
• Verify consistency between fetch function and webhook documentation

Tasks

• KNO-10168

---

Session info:

• Requested by: Chris Bell (chris@knock.app, @cjbell)
• Devin session: https://app.devin.ai/sessions/ad0ccfa6300943e9ba650d0536e97e72
• Related switchboard PR: https://github.com/knocklabs/switchboard/pull/4793

---

Note

Documents automatic Content-Type: application/json for requests with bodies in fetch and webhook steps, including override support and no default for GET/empty body.

• Docs:
  • content/designing-workflows/fetch-function.mdx:
    • Adds a new "Default headers" section explaining automatic Content-Type: application/json when a request body is present, ability to override via explicit header, and no default for GET/no-body.
  • content/integrations/webhook/overview.mdx:
    • Adds a matching "Default headers" section detailing the same default/override behavior and exception for GET/no-body.

^{Written by Cursor Bugbot for commit 6996ad5. This will update automatically on new commits. Configure here.}

[linear]

KNO-10168 [Switchboard] Add `Content-Type` header to fetch and webhook steps when a request body is included

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Project	Deployment	Preview	Comments	Updated (UTC)
docs	Ready	Preview	Comment	Oct 17, 2025 7:22pm

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[cellomatt]

Awesome!

Should we also document the User-Agent: Knock/1.0 (https://docs.knock.app/http-fetch-function) header?

(I'm not sure how that looks on a webhook send, actually)