http-mcp-headers

# HTTP MCP Header Secret Support - Implementation Summary This document demonstrates the complete implementation of HTTP MCP header secret support for the copilot engine. ## Problem Statement When using HTTP MCP tools with headers containing GitHub Actions secrets, the generated mcp-config.json needs to: 1. Extract secrets from headers (e.g., `${{ secrets.DD_API_KEY }}`) 2. Declare those env variables in the execution step 3. Configure the MCP config's "env" section to passthrough those variables 4. Use the passed variables in the headers section ## Example Workflow ```markdown on: workflow_dispatch: permissions: contents: read engine: copilot mcp-servers: datadog: type: http url: "https://mcp.datadoghq.com/api/unstable/mcp-server/mcp" headers: DD_API_KEY: "${{ secrets.DD_API_KEY }}" DD_APPLICATION_KEY: "${{ secrets.DD_APPLICATION_KEY }}" DD_SITE: "${{ secrets.DD_SITE || 'datadoghq.com' }}" allowed: - search_datadog_dashboards - search_datadog_slos - search_datadog_metrics - get_datadog_metric # Datadog Dashboard Search Search for Datadog dashboards and provide a summary. ``` ## Generated Output ### 1. MCP Config (mcp-config.json) ```json { "mcpServers": { "datadog": { "type": "http", "url": "https://mcp.datadoghq.com/api/unstable/mcp-server/mcp", "headers": { "DD_API_KEY": "${DD_API_KEY}", "DD_APPLICATION_KEY": "${DD_APPLICATION_KEY}", "DD_SITE": "${DD_SITE}" }, "tools": [ "search_datadog_dashboards", "search_datadog_slos", "search_datadog_metrics", "get_datadog_metric" ], "env": { "DD_API_KEY": "\\${DD_API_KEY}", "DD_APPLICATION_KEY": "\\${DD_APPLICATION_KEY}", "DD_SITE": "\\${DD_SITE}" } } } } ``` ### 2. Execution Step Environment Variables ```yaml env: DD_API_KEY: ${{ secrets.DD_API_KEY }} DD_APPLICATION_KEY: ${{ secrets.DD_APPLICATION_KEY }} DD_SITE: ${{ secrets.DD_SITE || 'datadoghq.com' }} GH_AW_MCP_CONFIG: /home/runner/.copilot/mcp-config.json COPILOT_GITHUB_TOKEN: ${{ secrets.COPILOT_GITHUB_TOKEN }} # ... other env vars ``` ## Implementation Details ### Key Functions 1. **extractSecretsFromValue(value string)** - Extracts secret expressions from a string - Parses `${{ secrets.VAR_NAME }}` patterns - Handles default values: `${{ secrets.VAR || 'default' }}` - Returns map of variable names to full expressions 2. **extractSecretsFromHeaders(headers map[string]string)** - Extracts all secrets from HTTP headers - Iterates through all header values - Collects all unique secret expressions - Returns consolidated map of secrets 3. **replaceSecretsWithEnvVars(value string, secrets map[string]string)** - Replaces secret expressions with env var references - Transforms `${{ secrets.DD_API_KEY }}` to `${DD_API_KEY}` - Used in MCP config headers rendering 4. **collectHTTPMCPHeaderSecrets(tools map[string]any)** - Collects secrets from all HTTP MCP tools - Scans all tools for HTTP MCP configurations - Extracts secrets from each tool's headers - Returns consolidated map for execution step env ### Rendering Logic #### In renderSharedMCPConfig (mcp-config.go): 1. **Extract secrets** when rendering HTTP MCP configs for copilot engine 2. **Add env section** to property order when secrets are found 3. **Render headers** with env var references instead of secret expressions 4. **Render env** with passthrough syntax (`\${VAR_NAME}`) #### In GetExecutionSteps (copilot_engine.go): 1. **Collect all HTTP MCP header secrets** from workflow tools 2. **Add to execution step env map** with secret expressions ## Security Benefits 1. **Secrets never appear in MCP config** - Only env var references 2. **Proper GitHub Actions secret handling** - Uses `${{ secrets.* }}` syntax 3. **Environment isolation** - Each MCP server receives only its required secrets 4. **Consistent pattern** - Matches existing GitHub remote MCP server implementation ## Test Coverage ### Unit Tests (mcp_http_headers_test.go) - extractSecretsFromValue - extractSecretsFromHeaders - replaceSecretsWithEnvVars - collectHTTPMCPHeaderSecrets - renderSharedMCPConfig with HTTP headers ### Integration Tests (copilot_mcp_http_integration_test.go) - Single HTTP MCP tool with secrets - Multiple HTTP MCP tools - HTTP MCP without secrets - Property ordering - Env variable sorting All tests pass ✓ --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/github) — claim your Tome and manage your conversions. <!-- tomevault:4.0:skill_md:2026-04-11 -->