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SEP-3149: Require Token Endpoint Auth Methods Supported in CIMD - #3149

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max-stytch wants to merge 11 commits into
modelcontextprotocol:mainfrom
max-stytch:max/token-endpoint-auth-method
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SEP-3149: Require Token Endpoint Auth Methods Supported in CIMD#3149
max-stytch wants to merge 11 commits into
modelcontextprotocol:mainfrom
max-stytch:max/token-endpoint-auth-method

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@max-stytch

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Motivation and Context

This SEP makes the token_endpoint_auth_methods_supported metadata parameter
a required property of MCP Client ID Metadata Documents (CIMD), and creates a
deprecation path for the singular token_endpoint_auth_method parameter,
mirroring the guidance in OpenID Connect RP Metadata Choices 1.0.
This enables a CIMD document to be published once and consumed by many
authorization servers with differing capabilities. It also deprecates the
implicit public-client default that applies when a document declares no
authentication method at all.

How Has This Been Tested?

Breaking Changes

Types of changes

  • Bug fix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • Breaking change (fix or feature that would cause existing functionality to change)
  • Documentation update

Checklist

  • I have read the MCP Documentation
  • My code follows the repository's style guidelines
  • New and existing tests pass locally
  • I have added appropriate error handling
  • I have added or updated documentation as needed

Additional context

@max-stytch max-stytch changed the title SEP: Require Token Endpoint Auth Methods Supported in CIMD SEP-3149: Require Token Endpoint Auth Methods Supported in CIMD Jul 28, 2026
Rename from the 0000 placeholder and update the title, PR link, and
lifecycle table entries per the PR-based SEP workflow.
Apply Prettier formatting to the SEP and regenerate the rendered SEP
documentation, navigation, and index entries.
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