Adding Custom Headers to MCP Connectors in Copilot Studio
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Configure server-level context for Copilot Studio MCP connectors by editing OpenAPI YAML, refreshing each agent, and adding the header as an input.
TL;DR
Copilot Studio MCP connectors have no UI for custom headers, so define them in the OpenAPI YAML under the /mcp POST endpoint, update the connector, remove and re-add it in each agent, then configure the header input with a value or PowerFX expression. Avoid X-prefixed names while the documented issue remains.
Original by Adi Leibowitz, on Microsoft Copilot Studio CAT. Read the original
This is our own summary, not a republication or full translation.
Governance takeaway
- Makers: Add server-level context such as a verified user rank as a custom header instead of a tool input, so the MCP server can apply consistent filtering across calls.
- Admins/CoE: Edit the custom connector OpenAPI YAML, update it, then remove and re-add the connector in every affected agent because an update alone is insufficient.
- Security/Compliance: Review custom headers used for authentication, roles, permissions, or feature flags, and avoid X-prefixed names while the documented connector issue remains.
Frequently asked questions
How do I add a user-level header to an MCP connector in Copilot Studio?
Edit the connector OpenAPI YAML under the /mcp POST endpoint, update it, then expose the header through the connector Inputs section.
Why must I remove and re-add an MCP connector after editing its OpenAPI YAML?
Copilot Studio recognizes the changed custom header only after the connector is removed and added again in each agent that uses it.
Are X-prefixed custom headers supported by MCP connectors in October 2025?
The documented October 2025 issue says X-prefixed headers are not working, so use names without the X-prefix until the issue is resolved.